Enable Roslyn compiler output caching in non-official builds

Directory.Build.props

@@ -15,6 +15,7 @@
     <!-- Propagate the configuration and platform to project references. When building in VS, this defaults to true.
          Explicitly setting it to false ensures projects are built in the corresponding configuration both in VS and on the command line. -->
     <ShouldUnsetParentConfigurationAndPlatform>false</ShouldUnsetParentConfigurationAndPlatform>
+    <EnableSourceLink Condition="'$(ROSLYN_CACHE_PATH)' != ''">false</EnableSourceLink>
   </PropertyGroup>
 
   <!-- We don't have RepoRoot or RepositoryEngineeringDir available at this point -->

eng/pipelines/coreclr/templates/roslyn-cache-stats.yml

@@ -0,0 +1,24 @@
+steps:
+  - script: |
+      set -euo pipefail
+
+      dotnet="$(Build.SourcesDirectory)/.dotnet/dotnet"
+      if [[ -z "${ROSLYN_CACHE_PATH:-}" ||
+            -z "${ROSLYN_CACHE_BUILD_START:-}" ||
+            ! -x "$dotnet" ]]; then
+          echo "Roslyn compiler cache statistics are unavailable."
+          exit 0
+      fi
+
+      sdkVersion="$("$dotnet" --version)"
+      compilerServer="$(Build.SourcesDirectory)/.dotnet/sdk/$sdkVersion/Roslyn/bincore/VBCSCompiler.dll"
+      if [[ ! -f "$compilerServer" ]]; then
+          echo "Roslyn compiler server not found at $compilerServer."
+          exit 0
+      fi
+
+      "$dotnet" "$compilerServer" \
+        "-cachestats:${ROSLYN_CACHE_BUILD_START}" \
+        "-cachepath:${ROSLYN_CACHE_PATH}" || true
+    displayName: Roslyn compiler cache stats
+    condition: always()

eng/pipelines/coreclr/templates/sccache-stats.yml

@@ -13,6 +13,8 @@ parameters:
 
 steps:
   - ${{ if and(or(eq(parameters.osGroup, 'linux'), eq(parameters.osGroup, 'freebsd'), eq(parameters.osGroup, 'openbsd'), eq(parameters.osGroup, 'osx')), or(eq(parameters.archType, 'x64'), eq(parameters.archType, 'arm64'))) }}:
+    - template: /eng/pipelines/coreclr/templates/roslyn-cache-stats.yml
+
     - script: sccache --show-stats || true
       displayName: Sccache stats
       condition: always()

eng/pipelines/coreclr/templates/setup-roslyn-cache.yml

@@ -0,0 +1,28 @@
+parameters:
+  archType: 'x64'
+  osGroup: 'linux'
+  nameSuffix: ''
+  osSubgroup: ''
+
+steps:
+  # Cache entries restored by pull request builds come only from the pull
+  # request itself or its target branch. This lets rolling builds seed the
+  # cache without allowing pull requests to modify caches used by main.
+  #
+  # The managed configuration is intentionally excluded. Roslyn's
+  # deterministic key includes the compilation options, and some pipeline
+  # legs override the matrix configuration in their build arguments.
+  - task: Cache@2
+    displayName: Roslyn compiler cache
+    continueOnError: true
+    inputs:
+      key: roslyn | v1 | ${{ parameters.osGroup }}${{ parameters.osSubgroup }} | ${{ parameters.archType }} | ${{ parameters.nameSuffix }} | "$(Build.BuildId)"
+      path: $(Pipeline.Workspace)/.roslyn-cache
+      restoreKeys: |
+        roslyn | v1 | ${{ parameters.osGroup }}${{ parameters.osSubgroup }} | ${{ parameters.archType }} | ${{ parameters.nameSuffix }}
+
+  - script: |
+      set -euo pipefail
+      echo "##vso[task.setvariable variable=ROSLYN_CACHE_PATH]$(Pipeline.Workspace)/.roslyn-cache"
+      echo "##vso[task.setvariable variable=ROSLYN_CACHE_BUILD_START]$(date -u +"%Y-%m-%dT%H:%M:%SZ")"
+    displayName: Configure Roslyn compiler cache

eng/pipelines/coreclr/templates/setup-sccache.yml

@@ -17,6 +17,13 @@ parameters:
 
 steps:
   - ${{ if and(or(eq(parameters.osGroup, 'linux'), eq(parameters.osGroup, 'freebsd'), eq(parameters.osGroup, 'openbsd'), eq(parameters.osGroup, 'osx')), or(eq(parameters.archType, 'x64'), eq(parameters.archType, 'arm64'))) }}:
+    - template: /eng/pipelines/coreclr/templates/setup-roslyn-cache.yml
+      parameters:
+        osGroup: ${{ parameters.osGroup }}
+        osSubgroup: ${{ parameters.osSubgroup }}
+        archType: ${{ parameters.archType }}
+        nameSuffix: ${{ parameters.nameSuffix }}
+
     # Set up the Azure Pipeline Cache for sccache's local cache directory.
     # Use a rolling key so each build can update the cache; restoreKeys
     # falls back to the most recent saved entry.