Merge pull request #1525 from vitek-karas/OpenInstallerTestSln

Setup environment to open the installer test sln

eng/build.ps1

@@ -66,14 +66,26 @@ $subsetCategory = $subsetCategory.ToLowerInvariant()
 if ($vs) {
   . $PSScriptRoot\common\tools.ps1
 
-  if (-Not (Test-Path $vs)) {
-    $vs = Join-Path "$PSScriptRoot\..\src\libraries" $vs | Join-Path -ChildPath "$vs.sln"
+  # Microsoft.DotNet.CoreSetup.sln is special - hosting tests are currently meant to run on the
+  # bootstrapped .NET Core, not on the live-built runtime.
+  if ([System.IO.Path]::GetFileName($vs) -ieq "Microsoft.DotNet.CoreSetup.sln") {
+    if (-Not (Test-Path $vs)) {
+      $vs = Join-Path "$PSScriptRoot\..\src\installer" $vs
+    }
+
+    # This tells .NET Core to use the bootstrapped runtime to run the tests
+    $env:DOTNET_ROOT=InitializeDotNetCli -install:$false
   }
+  else {
+    if (-Not (Test-Path $vs)) {
+      $vs = Join-Path "$PSScriptRoot\..\src\libraries" $vs | Join-Path -ChildPath "$vs.sln"
+    }
 
-  $archTestHost = if ($arch) { $arch } else { "x64" }
+    $archTestHost = if ($arch) { $arch } else { "x64" }
 
-  # This tells .NET Core to use the same dotnet.exe that build scripts use
-  $env:DOTNET_ROOT="$PSScriptRoot\..\artifacts\bin\testhost\netcoreapp5.0-Windows_NT-$configuration-$archTestHost";
+    # This tells .NET Core to use the same dotnet.exe that build scripts use
+    $env:DOTNET_ROOT="$PSScriptRoot\..\artifacts\bin\testhost\netcoreapp5.0-Windows_NT-$configuration-$archTestHost";
+  }
 
   # This tells MSBuild to load the SDK from the directory of the bootstrapped SDK
   $env:DOTNET_MSBUILD_SDK_RESOLVER_CLI_DIR=InitializeDotNetCli -install:$false