Fix IdeCore benchmark build isolation

eng/validate-benchmarks.ps1

@@ -20,10 +20,11 @@ $benchmarkProjects = @(
   @{ Project = "src/Razor/src/Compiler/perf/Microbenchmarks/Microsoft.AspNetCore.Razor.Microbenchmarks.Compiler.csproj"; Framework = "net10.0" }
   @{ Project = "src/Razor/src/Razor/benchmarks/Microsoft.AspNetCore.Razor.Microbenchmarks/Microsoft.AspNetCore.Razor.Microbenchmarks.csproj"; Framework = "net10.0"; HasValidationMode = $true }
   @{ Project = "src/Razor/src/Compiler/perf/Microsoft.AspNetCore.Razor.Microbenchmarks.Generator/Microsoft.AspNetCore.Razor.Microbenchmarks.Generator.csproj"; HasValidationMode = $true }
+  # Use a representative type to exercise the generated runner build without running the full benchmark suite.
+  @{ Project = "src/Tools/IdeCoreBenchmarks/IdeCoreBenchmarks.csproj"; Framework = "net10.0"; Filter = "*SegmentedArrayBenchmarks_Indexer*" }
 
   # These projects are excluded because their current benchmark harnesses do not
   # complete a Dry validation run in this script's execution model.
-  # @{ Project = "src/Tools/IdeCoreBenchmarks/IdeCoreBenchmarks.csproj"; Framework = "net10.0" }
   # @{ Project = "src/Tools/IdeBenchmarks/IdeBenchmarks.csproj" }
 )
 
@@ -65,7 +66,8 @@ foreach ($entry in $benchmarkProjects) {
 
   if ($ci) {
     # Keep the filter as one argument so PowerShell does not expand '*' into file names.
-    $args += "--filter=*"
+    $filter = if ($entry.ContainsKey("Filter")) { $entry["Filter"] } else { "*" }
+    $args += "--filter=$filter"
   }
 
   Write-Host "dotnet $($args -join ' ')"

src/Tools/IdeCoreBenchmarks/Program.cs

@@ -17,6 +17,9 @@ namespace IdeCoreBenchmarks
 {
     internal class Program
     {
+        private const string GlobalPropertiesToRemoveFromProjectReferencesEnvVariableName = "_GlobalPropertiesToRemoveFromProjectReferences";
+        private const string BenchmarkDotNetOutputProperties = "ArtifactsPath;OutDir;OutputPath;PublishDir";
+
         private class IgnoreReleaseOnly : ManualConfig
         {
             public IgnoreReleaseOnly()
@@ -37,10 +40,27 @@ public static string GetRoslynRootLocation([CallerFilePath] string sourceFilePat
             return Path.Combine(Path.GetDirectoryName(sourceFilePath), @"..\..\..");
         }
 
-        private static void Main(string[] args)
+        private static int Main(string[] args)
         {
             Environment.SetEnvironmentVariable(RoslynRootPathEnvVariableName, GetRoslynRootLocation());
-            new BenchmarkSwitcher(typeof(Program).Assembly).Run(args);
+            // BenchmarkDotNet gives its generated runner a single output directory through global
+            // MSBuild properties. If those properties flow into Roslyn's multi-targeted project graph,
+            // different projects and target frameworks share output and intermediate paths, causing
+            // file-write races and mixed-framework assemblies.
+            var existingProperties = Environment.GetEnvironmentVariable(GlobalPropertiesToRemoveFromProjectReferencesEnvVariableName);
+            var propertiesToRemove = string.IsNullOrEmpty(existingProperties)
+                ? BenchmarkDotNetOutputProperties
+                : $"{existingProperties};{BenchmarkDotNetOutputProperties}";
+            Environment.SetEnvironmentVariable(
+                GlobalPropertiesToRemoveFromProjectReferencesEnvVariableName,
+                propertiesToRemove);
+
+            var summaries = new BenchmarkSwitcher(typeof(Program).Assembly).Run(args);
+            return summaries.Any(summary =>
+                summary.HasCriticalValidationErrors ||
+                summary.Reports.Any(report => !report.BuildResult.IsBuildSuccess || !report.AllMeasurements.Any()))
+                ? 1
+                : 0;
         }
     }
 }