[main] UB Validate installer packages failing due to project file `Microsoft.DotNet.Installer.Tests.csproj` was not found

[Winniexu01]

https://dev.azure.com/dnceng/internal/_build/results?buildId=2704156&view=logs&j=f658f75f-a0a4-540f-a88e-b7eaa3543693&t=b99696ce-2d02-5cf0-c1d4-70dfd2b4d2eb (internal Microsoft link)

  Restore was successful.
  Restored /mnt/vss/_work/1/s/.packages/microsoft.dotnet.arcade.sdk/10.0.0-beta.25221.2/tools/Tools.proj (in 1.24 sec).
/mnt/vss/_work/1/s/.packages/microsoft.dotnet.arcade.sdk/10.0.0-beta.25221.2/tools/Build.proj(221,5): error MSB3202: The project file "test/Microsoft.DotNet.Installer.Tests/Microsoft.DotNet.Installer.Tests.csproj" was not found.
##[error].packages/microsoft.dotnet.arcade.sdk/10.0.0-beta.25221.2/tools/Build.proj(221,5): error MSB3202: The project file "test/Microsoft.DotNet.Installer.Tests/Microsoft.DotNet.Installer.Tests.csproj" was not found.

[NikolaMilosavljevic]

This was caused by dotnet/dotnet#306

This particular change in build.sh:

From:

    "$CLI_ROOT/dotnet" msbuild --restore "$project" $bl $targets "${properties[@]}"

To:

    "$CLI_ROOT/dotnet" \
      msbuild \
      --restore \
      "$arcadeBuildStepsDir/Build.proj" \
      "/p:Projects=$project" \
      /p:Configuration=$configuration \
      "/p:RepoRoot=$scriptroot/" \
      "-tl:off" \
      $bl \
      "${actions[@]}" \
      "${properties[@]}"

It's likely that this project path now needs to be absolute instead of relative: https://github.com/dotnet/dotnet/blob/cdd3eef3e3053cb776f066fde7b2f5a2b7ebe886/eng/pipelines/templates/steps/vmr-validate-installers.yml#L37

      --projects test/Microsoft.DotNet.Installer.Tests/Microsoft.DotNet.Installer.Tests.csproj \

[NikolaMilosavljevic]

Yeah, absolute path will fix it - will send PR soon.