CI: Cache CMake build

.github/workflows/cmake.yml

@@ -18,7 +18,7 @@ jobs:
             name: Linux
             cache-key: linux
             cmake-args: '-DPICO_SDK_PATH=$GITHUB_WORKSPACE/pico-sdk -DPICO_SDK_POST_LIST_DIRS=$GITHUB_WORKSPACE/pico-extras'
-            apt-packages: clang-tidy gcc-arm-none-eabi libnewlib-arm-none-eabi libstdc++-arm-none-eabi-newlib
+            apt-packages: ccache gcc-arm-none-eabi
 
     runs-on: ${{matrix.os}}
 
@@ -26,6 +26,15 @@ jobs:
       PICO_SDK_PATH: $GITHUB_WORKSPACE/pico-sdk
 
     steps:
+    - name: Compiler Cache
+      uses: actions/cache@v2
+      with:
+        path: /home/runner/.ccache
+        key: ccache-cmake-${{github.ref}}-${{github.sha}}
+        restore-keys: |
+          ccache-cmake-${{github.ref}}
+          ccache-cmake
+
     - uses: actions/checkout@v2
       with:
         submodules: true
@@ -44,7 +53,7 @@ jobs:
       with:
         repository: raspberrypi/pico-extras
         path: pico-extras
-        submodules: false  # lwip breaks audio submodule fetchin
+        submodules: false  # lwip breaks audio submodule fetching
 
     # Linux deps
     - name: Install deps
@@ -58,10 +67,12 @@ jobs:
     - name: Configure CMake
       shell: bash
       working-directory: ${{runner.workspace}}/build
-      run: cmake $GITHUB_WORKSPACE -DCMAKE_BUILD_TYPE=$BUILD_TYPE ${{matrix.cmake-args}}
+      run: cmake $GITHUB_WORKSPACE -DCMAKE_BUILD_TYPE=$BUILD_TYPE -DCMAKE_C_COMPILER_LAUNCHER=ccache -DCMAKE_CXX_COMPILER_LAUNCHER=ccache ${{matrix.cmake-args}}
 
     - name: Build
       working-directory: ${{runner.workspace}}/build
       shell: bash
       run: |
+        ccache --zero-stats || true
         cmake --build . --config $BUILD_TYPE -j 2
+        ccache --show-stats || true