Shorten NativeAOT and ReadyToRun build paths

src/BenchmarkDotNet/Templates/R2RCsProj.txt

@@ -18,6 +18,8 @@
     <StartupObject>BenchmarkDotNet.Autogenerated.UniqueProgramName</StartupObject>
     <!-- workaround for 'Found multiple publish output files with the same relative path.' error -->
     <ErrorOnDuplicatePublishOutputFiles>false</ErrorOnDuplicatePublishOutputFiles>
+    <!-- Shorten obj path to work around https://github.com/dotnet/runtime/issues/103625. -->
+    <IntermediateOutputPath>$([MSBuild]::NormalizeDirectory('$(MSBuildProjectDirectory)', 'o'))</IntermediateOutputPath>
   </PropertyGroup>
 
   <PropertyGroup>

src/BenchmarkDotNet/Toolchains/NativeAot/Generator.cs

@@ -135,7 +135,7 @@ protected override async ValueTask GenerateProjectAsync(BuildPartition buildPart
             await GenerateReflectionFileAsync(artifactsPaths, cancellationToken).ConfigureAwait(false);
         }
 
-        private string GenerateProjectForNuGetBuild(string projectFilePath, BuildPartition buildPartition, ArtifactsPaths artifactsPaths, ILogger logger) => $"""
+        internal string GenerateProjectForNuGetBuild(string projectFilePath, BuildPartition buildPartition, ArtifactsPaths artifactsPaths, ILogger logger) => $"""
             <Project Sdk="Microsoft.NET.Sdk">
               <PropertyGroup>
                 <OutputType>Exe</OutputType>
@@ -159,6 +159,8 @@ private string GenerateProjectForNuGetBuild(string projectFilePath, BuildPartiti
                 <EnsureNETCoreAppRuntime>false</EnsureNETCoreAppRuntime> <!-- workaround for 'This runtime may not be supported by.NET Core.' error -->
                 <ErrorOnDuplicatePublishOutputFiles>false</ErrorOnDuplicatePublishOutputFiles> <!-- workaround for 'Found multiple publish output files with the same relative path.' error -->
                 <ValidateExecutableReferencesMatchSelfContained>false</ValidateExecutableReferencesMatchSelfContained>
+                <!-- Shorten obj path to work around https://github.com/dotnet/runtime/issues/103625. -->
+                <IntermediateOutputPath>$([MSBuild]::NormalizeDirectory('$(MSBuildProjectDirectory)', 'o'))</IntermediateOutputPath>
                 {GetInstructionSetSettings(buildPartition)}
               </PropertyGroup>
               {GetRuntimeSettings(buildPartition.RepresentativeBenchmarkCase.Job.Environment.Gc, buildPartition.Resolver)}

tests/BenchmarkDotNet.Tests/AotProjectGeneratorTests.cs

@@ -0,0 +1,66 @@
+using BenchmarkDotNet.Configs;
+using BenchmarkDotNet.Helpers;
+using BenchmarkDotNet.Jobs;
+using BenchmarkDotNet.Loggers;
+using BenchmarkDotNet.Parameters;
+using BenchmarkDotNet.Running;
+using BenchmarkDotNet.Tests.Mocks;
+using BenchmarkDotNet.Toolchains;
+using BenchmarkDotNet.Toolchains.NativeAot;
+using System.Xml.Linq;
+
+namespace BenchmarkDotNet.Tests
+{
+    public class AotProjectGeneratorTests
+    {
+        private const string ExpectedIntermediateOutputPath = "$([MSBuild]::NormalizeDirectory('$(MSBuildProjectDirectory)', 'o'))";
+
+        [Fact]
+        public void NativeAotProjectUsesShortBuildPaths()
+        {
+            var config = ManualConfig.CreateEmpty().CreateImmutableConfig();
+            var benchmark = BenchmarkCase.Create(
+                new Descriptor(MockFactory.MockType, MockFactory.MockMethodInfo),
+                Job.Default,
+                ParameterInstances.Empty,
+                config);
+            var buildPartition = new BuildPartition(
+                [new BenchmarkBuildInfo(benchmark, config, 0, new([]))],
+                BenchmarkRunnerClean.DefaultResolver);
+            var generator = new Generator(
+                ilCompilerVersion: "",
+                runtimeFrameworkVersion: "",
+                targetFrameworkMoniker: "net10.0",
+                cliPath: "",
+                runtimeIdentifier: "win-x64",
+                feeds: new Dictionary<string, string>(),
+                useNuGetClearTag: false,
+                useTempFolderForRestore: false,
+                packagesRestorePath: "",
+                rootAllApplicationAssemblies: false,
+                ilcGenerateStackTraceData: true,
+                ilcOptimizationPreference: "Speed",
+                ilcInstructionSet: "");
+
+            string project = generator.GenerateProjectForNuGetBuild(
+                "Benchmarks.csproj",
+                buildPartition,
+                ArtifactsPaths.Empty,
+                NullLogger.Instance);
+
+            AssertShortIntermediatePath(XDocument.Parse(project));
+        }
+
+        [Fact]
+        public void ReadyToRunProjectUsesShortBuildPaths()
+        {
+            AssertShortIntermediatePath(XDocument.Parse(ResourceHelper.LoadTemplate("R2RCsProj.txt")));
+        }
+
+        private static void AssertShortIntermediatePath(XDocument project)
+        {
+            Assert.Equal(ExpectedIntermediateOutputPath, project.Descendants("IntermediateOutputPath").Single().Value);
+            Assert.Empty(project.Descendants("BaseIntermediateOutputPath"));
+        }
+    }
+}