github: Try to use ccache for the builds of LLVM

This should allow speeding up successive rebuilds of the same
build configuration, as long as the base LLVM version that is
being built is the same.

The second stage builds are run with

    CCACHE_COMPILERCHECK="%compiler% -v"

as the mtime of the compiler can change in successive rebuilds
of the first stage, even if the output binaries are identical.
(Although we could fix the timestamps when tarring the output.)

On the level of building LLVM, there is no significant measurable
difference in build speed between using
CCACHE_COMPILERCHECK="%compiler% -v" and CCACHE_COMPILERCHECK="none".

.github/workflows/build.yml

@@ -71,6 +71,12 @@ jobs:
     runs-on: ubuntu-20.04
     steps:
       - uses: actions/checkout@v4
+      - name: Setup ccache
+        uses: hendrikmuhs/[email protected]
+        with:
+          max-size: 1500M
+          key: linux-native
+          verbose: 1
       - name: Build
         env:
           LLVM_VERSION: ${{needs.prepare.outputs.LLVM_VERSION}}
@@ -83,7 +89,7 @@ jobs:
           # Skip dynamic library dependencies that might make it harder to
           # run the binaries on other distros (and that have little use within
           # llvm-mingw).
-          LLVM_CMAKEFLAGS="-DLLVM_ENABLE_LIBXML2=OFF -DLLVM_ENABLE_TERMINFO=OFF -DLLDB_ENABLE_PYTHON=OFF" ./build-all.sh $(pwd)/install/llvm-mingw --disable-clang-tools-extra
+          LLVM_CMAKEFLAGS="-DLLVM_ENABLE_LIBXML2=OFF -DLLVM_ENABLE_TERMINFO=OFF -DLLDB_ENABLE_PYTHON=OFF" COMPILER_LAUNCHER="ccache" ./build-all.sh $(pwd)/install/llvm-mingw --disable-clang-tools-extra
           .github/workflows/store-version.sh install/llvm-mingw/versions.txt
           RUN_I686=false RUN_X86_64=false ./run-tests.sh $(pwd)/install/llvm-mingw
           cd install
@@ -106,14 +112,20 @@ jobs:
     runs-on: ubuntu-20.04
     steps:
       - uses: actions/checkout@v4
+      - name: Setup ccache
+        uses: hendrikmuhs/[email protected]
+        with:
+          max-size: 500M
+          key: linux-cross-aarch64
+          verbose: 1
       - name: Build
         env:
           LLVM_VERSION: ${{needs.prepare.outputs.LLVM_VERSION}}
           MINGW_W64_VERSION: ${{needs.prepare.outputs.MINGW_W64_VERSION}}
           SOURCE_DATE_EPOCH: ${{needs.prepare.outputs.COMMIT_DATE_UNIX}}
         run: |
           sudo apt-get update && sudo apt-get install ninja-build g++-aarch64-linux-gnu
-          ./build-all.sh $(pwd)/install/llvm-mingw --disable-clang-tools-extra --no-runtimes --host=aarch64-linux-gnu
+          COMPILER_LAUNCHER="ccache" ./build-all.sh $(pwd)/install/llvm-mingw --disable-clang-tools-extra --no-runtimes --host=aarch64-linux-gnu
           .github/workflows/store-version.sh install/llvm-mingw/versions.txt
       - uses: actions/download-artifact@v4
         with:
@@ -190,6 +202,12 @@ jobs:
     runs-on: macos-14
     steps:
       - uses: actions/checkout@v4
+      - name: Setup ccache
+        uses: hendrikmuhs/[email protected]
+        with:
+          max-size: 750M
+          key: macos
+          verbose: 1
       - name: Build
         env:
           LLVM_VERSION: ${{needs.prepare.outputs.LLVM_VERSION}}
@@ -204,7 +222,7 @@ jobs:
           # form. Therefore, autodetection will pick them up, but linking
           # universal binaries fails as those libraries are unavailable in the
           # other (arm64) architecture form.
-          MACOS_REDIST=1 LLVM_CMAKEFLAGS="-DLLVM_ENABLE_ZSTD=OFF -DLLDB_ENABLE_PYTHON=OFF" ./build-all.sh $(pwd)/install/llvm-mingw --disable-clang-tools-extra
+          MACOS_REDIST=1 LLVM_CMAKEFLAGS="-DLLVM_ENABLE_ZSTD=OFF -DLLDB_ENABLE_PYTHON=OFF" COMPILER_LAUNCHER="ccache" ./build-all.sh $(pwd)/install/llvm-mingw --disable-clang-tools-extra
           .github/workflows/store-version.sh install/llvm-mingw/versions.txt
           RUN_I686=false RUN_X86_64=false ./run-tests.sh $(pwd)/install/llvm-mingw
           cd install
@@ -248,7 +266,14 @@ jobs:
             toolchain:p
             cmake:p
             ninja:p
+            ccache:p
       - uses: actions/checkout@v4
+      - name: Setup ccache
+        uses: hendrikmuhs/[email protected]
+        with:
+          max-size: 600M
+          key: msys2-${{matrix.sys}}
+          verbose: 1
       - name: Build
         env:
           LLVM_VERSION: ${{needs.prepare.outputs.LLVM_VERSION}}
@@ -260,7 +285,7 @@ jobs:
           if [ "${{matrix.sys}}" = "mingw64" ]; then
               ARGS="--disable-dylib"
           fi
-          ./build-all.sh $(pwd)/install/llvm-mingw --disable-clang-tools-extra --disable-lldb $ARGS
+          COMPILER_LAUNCHER="ccache" ./build-all.sh $(pwd)/install/llvm-mingw --disable-clang-tools-extra --disable-lldb $ARGS
           .github/workflows/store-version.sh install/llvm-mingw/versions.txt
           ./copy-msys-dependencies.sh $(pwd)/install/llvm-mingw ${{matrix.sys}}
           ./run-tests.sh $(pwd)/install/llvm-mingw
@@ -301,6 +326,12 @@ jobs:
           sudo mv llvm-mingw* /opt/llvm-mingw
           echo /opt/llvm-mingw/bin >> $GITHUB_PATH
       - uses: actions/checkout@v4
+      - name: Setup ccache
+        uses: hendrikmuhs/[email protected]
+        with:
+          max-size: 800M
+          key: linux-cross-windows-${{matrix.arch}}
+          verbose: 1
       - name: Build
         env:
           LLVM_VERSION: ${{needs.prepare.outputs.LLVM_VERSION}}
@@ -311,7 +342,7 @@ jobs:
           BUILD_DATE: ${{needs.prepare.outputs.BUILD_DATE}}
         run: |
           sudo apt-get update && sudo apt-get install autoconf-archive ninja-build
-          ./build-cross-tools.sh /opt/llvm-mingw $(pwd)/install/llvm-mingw ${{matrix.arch}} --with-python
+          COMPILER_LAUNCHER="ccache" CCACHE_COMPILERCHECK="%compiler% -v" ./build-cross-tools.sh /opt/llvm-mingw $(pwd)/install/llvm-mingw ${{matrix.arch}} --with-python
           .github/workflows/store-version.sh install/llvm-mingw/versions.txt
           cd install
           NAME=llvm-mingw-$TAG-${{matrix.crt}}-${{matrix.arch}}