Setup sccache for SDK job

We do a small bit of C/C++ building in the SDK job which could benefit
from also using sccache. This sets the cache up with the associated
steps for fallback to disk cache and workspace hash computation.

Author: brianmichel

.github/workflows/swift-toolchain.yml

@@ -2278,6 +2278,30 @@ jobs:
           ref: ${{ inputs.swift_testing_revision }}
           path: ${{ github.workspace }}/SourceCache/swift-testing
           show-progress: false
+      - uses: actions/[email protected]
+        with:
+          path: ${{ github.workspace }}/SourceCache/swift-build
+          show-progress: false
+
+      - name: Compute workspace hash
+        id: workspace_hash
+        run: |
+          $stringAsStream = [System.IO.MemoryStream]::new()
+          $writer = [System.IO.StreamWriter]::new($stringAsStream)
+          $writer.write("${{ github.workspace }}")
+          $writer.Flush()
+          $stringAsStream.Position = 0
+          $hash = (Get-FileHash -Algorithm SHA256 -InputStream $stringAsStream).Hash
+          echo "hash=$hash" >> $env:GITHUB_OUTPUT
+
+      - name: Setup sccache
+        uses: ./SourceCache/swift-build/.github/actions/setup-sccache
+        with:
+          s3-bucket: ${{ vars.SCCACHE_S3_BUCKET }}
+          aws-region: ${{ vars.SCCACHE_AWS_REGION }}
+          aws-arn: ${{ vars.SCCACHE_AWS_ARN }}
+          disk-max-size: 500M
+          disk-cache-key: ${{ steps.workspace_hash.outputs.hash }}-${{ matrix.os }}-${{ matrix.arch }}-sdk
 
       - name: Setup environment
         if: matrix.os != 'Android' || inputs.build_android
@@ -2412,9 +2436,11 @@ jobs:
                 -D BUILD_SHARED_LIBS=YES `
                 -D CMAKE_BUILD_TYPE=Release `
                 -D CMAKE_C_COMPILER=${{ matrix.cc }} `
+                -D CMAKE_C_COMPILER_LAUNCHER=sccache `
                 -D CMAKE_C_COMPILER_TARGET=${{ matrix.triple }} `
                 -D CMAKE_C_FLAGS="${{ matrix.cflags }}" `
                 -D CMAKE_CXX_COMPILER=${{ matrix.cxx }} `
+                -D CMAKE_CXX_COMPILER_LAUNCHER=sccache `
                 -D CMAKE_CXX_COMPILER_TARGET=${{ matrix.triple }} `
                 -D CMAKE_CXX_FLAGS="${{ matrix.cxxflags }}" `
                 -D CMAKE_INSTALL_PREFIX=${{ github.workspace }}/BuildRoot/Library/Developer/Platforms/${{ matrix.os }}.platform/Developer/SDKs/${{ matrix.os }}.sdk/usr `
@@ -2554,9 +2580,11 @@ jobs:
                 -D CMAKE_BUILD_TYPE=Release `
                 -D CMAKE_BUILD_WITH_INSTALL_RPATH=YES `
                 -D CMAKE_C_COMPILER=${{ matrix.cc }} `
+                -D CMAKE_C_COMPILER_LAUNCHER=sccache `
                 -D CMAKE_C_COMPILER_TARGET=${{ matrix.triple }} `
                 -D CMAKE_C_FLAGS="${{ matrix.cflags }}" `
                 -D CMAKE_CXX_COMPILER=${{ matrix.cxx }} `
+                -D CMAKE_CXX_COMPILER_LAUNCHER=sccache `
                 -D CMAKE_CXX_COMPILER_TARGET=${{ matrix.triple }} `
                 -D CMAKE_CXX_FLAGS="${{ matrix.cxxflags }}" `
                 -D CMAKE_INSTALL_BINDIR=$XCTestBinDir `
@@ -2621,6 +2649,7 @@ jobs:
                 -D CMAKE_BUILD_TYPE=Release `
                 -D CMAKE_BUILD_WITH_INSTALL_RPATH=YES `
                 -D CMAKE_CXX_COMPILER=${{ matrix.cxx }} `
+                -D CMAKE_CXX_COMPILER_LAUNCHER=sccache `
                 -D CMAKE_CXX_COMPILER_TARGET=${{ matrix.triple }} `
                 -D CMAKE_CXX_FLAGS="${{ matrix.cxxflags }}" `
                 -D CMAKE_INSTALL_BINDIR=$TestingBinDir `