Force /p:PortableBuild=true, for cases where we overrode the RID.

[directhex]

As-is, the build will fail on portable RID platforms because without /p:PortableBuild=true, the CrossGen2 nupkg gets imported twice, which causes a build failure due to an SDK bug.

Closes: dotnet/source-build#3150

[MichaelSimons]

@crummel can you please review this and merge if you approve. TIA.

[MichaelSimons]

Friendly ping @crummel.

[corngood]

I'm having this same problem on https://github.com/dotnet/dotnet/releases/tag/v8.0.0 when building linux-x64.

I'm using nixos. If I build normally on my machine, the rid it uses is nixos-24.05-x64. If I build in a nix sandbox, /etc/os-release is unavailable, so it uses linux-x64 and this error occurs. This also happens if I build with TargetRid=linux-x64 or PortableBuild=true.

This is enough to make it build with PortableBuild=true, which works both inside and outside the sandbox:

diff --git a/repo-projects/aspnetcore.proj b/repo-projects/aspnetcore.proj
index e3f4b1664a..947532add9 100644
--- a/repo-projects/aspnetcore.proj
+++ b/repo-projects/aspnetcore.proj
@@ -8,6 +8,7 @@
     <OverrideTargetRid Condition="'$(TargetOS)' == 'Windows_NT'">win-$(Platform)</OverrideTargetRid>
     <_portableRidOverridden Condition="'$(TargetRid)' != '$(OverrideTargetRid)'">true</_portableRidOverridden>
     <_portableRidOverridden Condition="'$(TargetRid)' == '$(OverrideTargetRid)'">false</_portableRidOverridden>
+    <_portableRidOverridden Condition="'$(PortableBuild)' != ''">$(PortableBuild)</_portableRidOverridden>
 
     <!-- StandardSourceBuildArgs include -publish which is not supported by the aspnetcore build script. -->
     <BuildCommandArgs>$(StandardSourceBuildArgs.Replace('--publish', ''))</BuildCommandArgs>

However, I feel like I don't fully understand what's going on here. Anyone have any advice?