Add VMR leg that builds test projects

eng/pipelines/templates/stages/vmr-build.yml

@@ -374,6 +374,16 @@ stages:
         targetOS: linux
         targetArchitecture: x64
 
+    - template: ../jobs/vmr-build.yml
+      parameters:
+        buildName: Windows_BuildTests
+        isBuiltFromVmr: ${{ parameters.isBuiltFromVmr }}
+        vmrBranch: ${{ variables.VmrBranch }}
+        pool: ${{ parameters.pool_Windows }}
+        targetOS: windows
+        targetArchitecture: x64
+        extraProperties: /p:DotNetBuildTests=true
+
 #### VERTICAL BUILD (Official) ####
 - ${{ if not(parameters.isSourceOnlyBuild) }}:
   - stage: VMR_Vertical_Build

src/SourceBuild/content/repo-projects/sdk.proj

@@ -3,6 +3,9 @@
   <PropertyGroup>
     <LogVerbosityOptOut>true</LogVerbosityOptOut>
 
+    <!-- Tests are only building on Windows - https://github.com/dotnet/source-build/issues/4882 -->
+    <DotNetBuildTestsOptOut Condition="'$(OS)' != 'Windows_NT'">true</DotNetBuildTestsOptOut>
+
     <BuildArgs Condition="'$(TargetOS)' == 'windows'">$(BuildArgs) -nativeToolsOnMachine</BuildArgs>
     <BuildArgs>$(BuildArgs) /p:PackageProjectUrl=https://github.com/dotnet/sdk</BuildArgs>
     <BuildArgs>$(BuildArgs) /p:PortableRid=$(PortableRid)</BuildArgs>

src/SourceBuild/content/repo-projects/winforms.proj

@@ -3,6 +3,9 @@
   <PropertyGroup>
     <LogVerbosityOptOut>true</LogVerbosityOptOut>
 
+    <!-- Tests are failing to build: https://github.com/dotnet/source-build/issues/4875 -->
+    <DotNetBuildTestsOptOut>true</DotNetBuildTestsOptOut>
+
     <BuildArgs>$(BuildArgs) $(FlagParameterPrefix)v $(LogVerbosity)</BuildArgs>
     <BuildArgs>$(BuildArgs) $(FlagParameterPrefix)NativeToolsOnMachine</BuildArgs>
   </PropertyGroup>