Use BaseOS instead of TargetRid when its available (#76838)

src/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/Microsoft.CodeAnalysis.LanguageServer.csproj

@@ -45,12 +45,13 @@
     <PublishDir Condition="'$(RuntimeIdentifier)' == ''">$(ArtifactsDir)/LanguageServer/$(Configuration)/$(TargetFramework)/neutral</PublishDir>
 
     <!-- List of runtime identifiers that we want to publish an executable for. -->
-    <!-- When building a VMR vertical, we don't need to pack everything. Just pack the passed in TargetRid.
-         TargetRid is provided to roslyn via the build arguments passed in the VMR orchestrator's repo project.
+    <!-- When building a VMR vertical, we don't need to pack everything. Just pack the passed in TargetRid or BaseOS.
+         TargetRid and BaseOS are provided to roslyn via the build arguments passed in the VMR orchestrator's repo project.
          https://github.com/dotnet/dotnet/blob/main/repo-projects/roslyn.proj. For definitions of the TargetRid
          and other common properties, see https://github.com/dotnet/arcade/blob/main/Documentation/UnifiedBuild/Unified-Build-Controls.md -->
     <RuntimeIdentifiers Condition="'$(TargetRid)' != ''">$(TargetRid)</RuntimeIdentifiers>
-    <RuntimeIdentifiers Condition="'$(TargetRid)' == ''">win-x64;win-arm64;linux-x64;linux-arm64;linux-musl-x64;linux-musl-arm64;osx-x64;osx-arm64</RuntimeIdentifiers>
+    <RuntimeIdentifiers Condition="'$(BaseOS)' != ''">$(BaseOS)</RuntimeIdentifiers>
+    <RuntimeIdentifiers Condition="'$(TargetRid)' == '' and '$(BaseOS)' == ''">win-x64;win-arm64;linux-x64;linux-arm64;linux-musl-x64;linux-musl-arm64;osx-x64;osx-arm64</RuntimeIdentifiers>
     <!-- Publish ready to run executables when we're publishing platform specific executables. -->
     <PublishReadyToRun Condition="'$(RuntimeIdentifier)' != '' AND '$(Configuration)' == 'Release' ">true</PublishReadyToRun>
   </PropertyGroup>