[ci] Build without -m:1. (#941)

`dotnet build Java.Interop.sln` didn't work unless `-m:1` was used:

	% make prepare-core JI_MAX_JDK=8
	% dotnet build -target:Prepare -p:MaxJdkVersion=8 Java.Interop.sln
	% dotnet build Java.Interop.sln
	…
	…/tests/Java.Interop.Export-Tests/Java.Interop.Export-Tests.csproj(35,5): error MSB3073: The command ""/Users/jon/android-toolchain/jdk-1.8/bin/javac" -classpath …" exited with code 1.
	…/tests/Java.Interop.Export-Tests/Java.Interop.Export-Tests.csproj(35,5): error MSB3073: The command ""/Users/jon/android-toolchain/jdk-1.8/bin/javac" -classpath …" exited with code 1.
	…/tests/Java.Interop-Tests/Java.Interop-Tests.csproj(60,5): error MSB3073: The command ""/Users/jon/android-toolchain/jdk-1.8/bin/javac" -source 1.8 -target 1.8 -bootclasspath …" exited with code 1.
	…/tests/Java.Interop-Tests/Java.Interop-Tests.csproj(60,5): error MSB3073: The command ""/Users/jon/android-toolchain/jdk-1.8/bin/javac" -source 1.8 -target 1.8 -bootclasspath …" exited with code 1.

Using `dotnet build -m:1` avoids the above MSB3073 errors; see also
commit 1de5501, which added `-m:1` to CI builds.

Fix these parallel build issues so that `-m:1` isn't needed.  This is
principally done by removing `Java.Interop.BootstrapTasks.csproj`
from `Java.Interop.sln`, and adding it to a new
`Java.Interop.BootstrapTasks.sln` solution.  The `Prepare` target is
updated to explicitly Restore and Build the new
`Java.Interop.BootstrapTasks.dll` solution.

Note that the Restore and Build target invocations must be separate;
using [`Targets="Restore;Build"` will not work][0].

Update `Java.Interop.BootstrapTasks.csproj` to *no longer* `<Import/>`
`VersionInfo.targets`, as this causes a circular dependency
(`VersionInfo.targets` uses tasks from
`Java.Interop.BootstrapTasks.dll`).  This is fine, as
`Java.Interop.BootstrapTasks.dll` doesn't need to be versioned.

Review our custom `.targets` files, and replace
`BeforeTargets="BeforeBuild"` with `BeforeTargets="Build"` or
`BeforeTargets="BeforeCompile"` (as appropriate).
Building before the `BeforeBuild` target is problematic, as the
`BeforeBuild` target runs before `@(ProjectReference)`d projects are
built, meaning dependencies may not exist.  (Oops.)

TODO: Instead of having two `.sln` files, try to instead use
`<UsingTask/>` with `AssemblyFile` and `TasFactory` set, as done in
[rainersigwald/build-task-in-solution-demo][1] and the
[`InvokeCustomTaskDemo` target][2].  This *may* avoid the need for
a separate `.sln` (and `Prepare` target invocation?).

[0]: dotnet/msbuild#2811 (comment)
[1]: https://github.com/rainersigwald/build-task-in-solution-demo
[2]: https://github.com/rainersigwald/build-task-in-solution-demo/blob/17508937bb9edb0b817820146f85adf0da331515/Task/DemoFunctionality.targets#L4-L10

Java.Interop.sln

@@ -77,8 +77,6 @@ Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Java.Interop.Tools.JavaCall
 EndProject
 Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Java.Interop.GenericMarshaler", "src\Java.Interop.GenericMarshaler\Java.Interop.GenericMarshaler.csproj", "{D1243BAB-23CA-4566-A2A3-3ADA2C2DC3AF}"
 EndProject
-Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Java.Interop.BootstrapTasks", "build-tools\Java.Interop.BootstrapTasks\Java.Interop.BootstrapTasks.csproj", "{3E8E5C8C-59A6-4A9A-B55D-46AB14431B2A}"
-EndProject
 Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Xamarin.Android.Tools.AndroidSdk", "external\xamarin-android-tools\src\Xamarin.Android.Tools.AndroidSdk\Xamarin.Android.Tools.AndroidSdk.csproj", "{E34BCFA0-CAA4-412C-AA1C-75DB8D67D157}"
 EndProject
 Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Java.Interop.Tools.JavaSource-Tests", "tests\Java.Interop.Tools.JavaSource-Tests\Java.Interop.Tools.JavaSource-Tests.csproj", "{093B5E94-7FB7-499F-9C11-30944BAFEE25}"
@@ -242,10 +240,6 @@ Global
 		{D1243BAB-23CA-4566-A2A3-3ADA2C2DC3AF}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{D1243BAB-23CA-4566-A2A3-3ADA2C2DC3AF}.Release|Any CPU.ActiveCfg = Release|Any CPU
 		{D1243BAB-23CA-4566-A2A3-3ADA2C2DC3AF}.Release|Any CPU.Build.0 = Release|Any CPU
-		{3E8E5C8C-59A6-4A9A-B55D-46AB14431B2A}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
-		{3E8E5C8C-59A6-4A9A-B55D-46AB14431B2A}.Debug|Any CPU.Build.0 = Debug|Any CPU
-		{3E8E5C8C-59A6-4A9A-B55D-46AB14431B2A}.Release|Any CPU.ActiveCfg = Release|Any CPU
-		{3E8E5C8C-59A6-4A9A-B55D-46AB14431B2A}.Release|Any CPU.Build.0 = Release|Any CPU
 		{E34BCFA0-CAA4-412C-AA1C-75DB8D67D157}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
 		{E34BCFA0-CAA4-412C-AA1C-75DB8D67D157}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{E34BCFA0-CAA4-412C-AA1C-75DB8D67D157}.Release|Any CPU.ActiveCfg = Release|Any CPU
@@ -338,7 +332,6 @@ Global
 		{52C7D9B6-E8C8-47D0-9471-652D278D7D77} = {C8F58966-94BF-407F-914A-8654F8B8AE3B}
 		{58B564A1-570D-4DA2-B02D-25BDDB1A9F4F} = {271C9F30-F679-4793-942B-0D9527CB3E2F}
 		{D1243BAB-23CA-4566-A2A3-3ADA2C2DC3AF} = {4C173212-371D-45D8-BA83-9226194F48DC}
-		{3E8E5C8C-59A6-4A9A-B55D-46AB14431B2A} = {172B608B-E6F3-41CC-9949-203A76BA247C}
 		{E34BCFA0-CAA4-412C-AA1C-75DB8D67D157} = {172B608B-E6F3-41CC-9949-203A76BA247C}
 		{093B5E94-7FB7-499F-9C11-30944BAFEE25} = {271C9F30-F679-4793-942B-0D9527CB3E2F}
 		{0E3AF6C1-7638-464D-9174-485D494499DC} = {C8F58966-94BF-407F-914A-8654F8B8AE3B}

build-tools/Java.Interop.BootstrapTasks/Java.Interop.BootstrapTasks.csproj

@@ -18,6 +18,4 @@
     </ProjectReference>
   </ItemGroup>
 
-  <Import Project="$(MSBuildThisFileDirectory)..\scripts\VersionInfo.targets" />
-
 </Project>

build-tools/Java.Interop.BootstrapTasks/Java.Interop.BootstrapTasks.sln

@@ -0,0 +1,31 @@
+
+Microsoft Visual Studio Solution File, Format Version 12.00
+# Visual Studio Version 17
+VisualStudioVersion = 17.1.32104.313
+MinimumVisualStudioVersion = 10.0.40219.1
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Java.Interop.BootstrapTasks", "Java.Interop.BootstrapTasks.csproj", "{47C54705-71BA-455D-9F72-780487DE861C}"
+EndProject
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Xamarin.Android.Tools.AndroidSdk", "..\..\external\xamarin-android-tools\src\Xamarin.Android.Tools.AndroidSdk\Xamarin.Android.Tools.AndroidSdk.csproj", "{2F8744CF-C265-440A-B976-DEC021324A3E}"
+EndProject
+Global
+	GlobalSection(SolutionConfigurationPlatforms) = preSolution
+		Debug|Any CPU = Debug|Any CPU
+		Release|Any CPU = Release|Any CPU
+	EndGlobalSection
+	GlobalSection(ProjectConfigurationPlatforms) = postSolution
+		{47C54705-71BA-455D-9F72-780487DE861C}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{47C54705-71BA-455D-9F72-780487DE861C}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{47C54705-71BA-455D-9F72-780487DE861C}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{47C54705-71BA-455D-9F72-780487DE861C}.Release|Any CPU.Build.0 = Release|Any CPU
+		{2F8744CF-C265-440A-B976-DEC021324A3E}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{2F8744CF-C265-440A-B976-DEC021324A3E}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{2F8744CF-C265-440A-B976-DEC021324A3E}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{2F8744CF-C265-440A-B976-DEC021324A3E}.Release|Any CPU.Build.0 = Release|Any CPU
+	EndGlobalSection
+	GlobalSection(SolutionProperties) = preSolution
+		HideSolutionNode = FALSE
+	EndGlobalSection
+	GlobalSection(ExtensibilityGlobals) = postSolution
+		SolutionGuid = {8C64DB4C-E064-43CA-B1AB-100760FEF870}
+	EndGlobalSection
+EndGlobal

build-tools/automation/templates/core-build.yaml

@@ -19,4 +19,4 @@ steps:
   displayName: Build Solution
   inputs:
     projects: Java.Interop.sln
-    arguments: '-c $(Build.Configuration) -m:1'
+    arguments: '-c $(Build.Configuration)'

build-tools/scripts/Prepare.targets

@@ -6,9 +6,11 @@
   <UsingTask AssemblyFile="$(_TopDir)\bin\Build$(Configuration)\Java.Interop.BootstrapTasks.dll" TaskName="Java.Interop.BootstrapTasks.JdkInfo" />
   <Target Name="Prepare">
     <Exec Command="git submodule update --init --recursive" WorkingDirectory="$(_TopDir)" />
-    <MSBuild Projects="$(MSBuildThisFileDirectory)..\..\build-tools\Java.Interop.BootstrapTasks\Java.Interop.BootstrapTasks.csproj"
-        Targets="Build;GenerateVersionInfo"
-        RunEachTargetSeparately="true"
+    <MSBuild Projects="$(MSBuildThisFileDirectory)..\..\build-tools\Java.Interop.BootstrapTasks\Java.Interop.BootstrapTasks.sln"
+        Targets="Restore"
+    />
+    <MSBuild Projects="$(MSBuildThisFileDirectory)..\..\build-tools\Java.Interop.BootstrapTasks\Java.Interop.BootstrapTasks.sln"
+        Targets="Build"
     />
     <PropertyGroup>
       <_MaxJdk>$(MaxJdkVersion)</_MaxJdk>

tests/Java.Interop-Tests/Java.Interop-Tests.csproj

@@ -50,7 +50,7 @@
     <JavaInteropTestJar Include="$(MSBuildThisFileDirectory)java\com\xamarin\interop\TestType.java" />
   </ItemGroup>
 
-  <Target Name="BuildInteropTestJar" BeforeTargets="BeforeBuild" Inputs="@(JavaInteropTestJar)" Outputs="$(OutputPath)interop-test.jar">
+  <Target Name="BuildInteropTestJar" BeforeTargets="Build" Inputs="@(JavaInteropTestJar)" Outputs="$(OutputPath)interop-test.jar">
     <MakeDir Directories="$(IntermediateOutputPath)it-classes" />
     <Exec Command="&quot;$(JavaCPath)&quot; $(_JavacSourceOptions) -d &quot;$(IntermediateOutputPath)it-classes&quot; -classpath &quot;$(OutputPath)../$(Configuration)/java-interop.jar&quot; @(JavaInteropTestJar->'%(Identity)', ' ')" />
     <Exec Command="&quot;$(JarPath)&quot; cf &quot;$(OutputPath)interop-test.jar&quot; -C &quot;$(IntermediateOutputPath)it-classes&quot; ." />

tests/Java.Interop.Export-Tests/Java.Interop.Export-Tests.csproj

@@ -30,7 +30,7 @@
     <JavaExportTestJar Include="$(MSBuildThisFileDirectory)java\com\xamarin\interop\export\ExportType.java" />
   </ItemGroup>
 
-  <Target Name="BuildExportTestJar" BeforeTargets="BeforeBuild" Inputs="@(JavaExportTestJar)" Outputs="$(OutputPath)export-test.jar">
+  <Target Name="BuildExportTestJar" BeforeTargets="Build" Inputs="@(JavaExportTestJar)" Outputs="$(OutputPath)export-test.jar">
     <MakeDir Directories="$(IntermediateOutputPath)et-classes" />
     <Exec Command="&quot;$(JavaCPath)&quot; -classpath &quot;$(OutputPath)../$(Configuration)/java-interop.jar&quot; $(_JavacSourceOptions) -d &quot;$(IntermediateOutputPath)et-classes&quot; @(JavaExportTestJar->'%(Identity)', ' ')" />
     <Exec Command="&quot;$(JarPath)&quot; cf &quot;$(OutputPath)export-test.jar&quot; -C &quot;$(IntermediateOutputPath)et-classes&quot; ." />

tests/Xamarin.Android.Tools.Bytecode-Tests/Xamarin.Android.Tools.Bytecode-Tests.targets

@@ -13,7 +13,7 @@
   </ItemGroup>
 
   <Target Name="BuildClasses"
-        BeforeTargets="BeforeBuild"
+        BeforeTargets="BeforeCompile"
         Inputs="@(TestJar);@(TestJarNoParameters)"
         Outputs="@(_BuildClassOutputs)">
     <MakeDir Directories="$(IntermediateOutputPath)classes" />
@@ -28,7 +28,7 @@
   -->
   <Target Name="BuildKotlinClasses"
         Condition=" '$(KotlinCPath)' != '' "
-        BeforeTargets="BeforeBuild"
+        BeforeTargets="Build"
         Inputs="@(TestKotlinJar)"
         Outputs="@(TestKotlinJar->'%(RecursiveDir)%(Filename).class')">
     <Exec Command="&quot;$(KotlinCPath)&quot; @(TestKotlinJar->'%(Identity)', ' ') -d &quot;kotlin&quot;" />