Add ccache caching to Linux GitHub Actions.

.github/workflows/linux_server_build.yml

@@ -118,6 +118,8 @@ jobs:
         echo "JOB_NAME=${{matrix.os}}, ${{matrix.arch}}" >> $GITHUB_ENV
 
         echo "CMAKE_BUILD_EXTRA=-- -j$(nproc)" >> $GITHUB_ENV
+        # Transparently enable ccache
+        echo "PATH=/usr/lib/ccache:/usr/local/opt/ccache/libexec:$PATH" >> $GITHUB_ENV
 
         if [[ "${{ matrix.os }}" =~ "ubuntu" || "${{ matrix.os }}" =~ "debian" ]]; then
           echo "INSTALLER_EXT=deb" >> $GITHUB_ENV
@@ -208,6 +210,11 @@ jobs:
         submodules: false
         fetch-depth: 1
 
+    - name: Enable ccache
+      uses: hendrikmuhs/ccache-action@v1.2
+      with:
+        key: ${{matrix.os}}-${{matrix.arch}}
+
     - name: Create Build Environment
       shell: bash
       run: mkdir build

.github/workflows/master_build.yml

@@ -71,6 +71,8 @@ jobs:
           echo "PYTHON_EXEC=python3" >> $GITHUB_ENV
           echo "INSTALLER_EXT=tgz" >> $GITHUB_ENV
           echo "CMAKE_BUILD_EXTRA=-- -j$(nproc)" >> $GITHUB_ENV
+          # Transparently enable ccache
+          echo "PATH=/usr/lib/ccache:/usr/local/opt/ccache/libexec:$PATH" >> $GITHUB_ENV
           echo "CMAKE_EXTRA=-DOVERTE_CPU_ARCHITECTURE=-msse3 -DBUILD_TOOLS:BOOLEAN=FALSE -DHIFI_PYTHON_EXEC:FILEPATH=$(which python3)" >> $GITHUB_ENV
         fi
         # Mac build variables
@@ -125,6 +127,11 @@ jobs:
         submodules: false
         fetch-depth: 1
 
+    - name: Enable ccache
+      uses: hendrikmuhs/ccache-action@v1.2
+      with:
+        key: ${{matrix.os}}-${{matrix.arch}}
+
     - name: Install dependencies
       shell: bash
       if: startsWith(matrix.os, 'ubuntu') || contains(matrix.os, 'debian') || startsWith(matrix.os, 'macOS')

.github/workflows/pr_build.yml

@@ -90,6 +90,8 @@ jobs:
           echo "CMAKE_BUILD_EXTRA=-- -j$(nproc)" >> $GITHUB_ENV
           # Don't optimize builds to save build time.
           echo "OVERTE_OPTIMIZE=false" >> $GITHUB_ENV
+          # Transparently enable ccache
+          echo "PATH=/usr/lib/ccache:/usr/local/opt/ccache/libexec:$PATH" >> $GITHUB_ENV
           # Starting with Ubuntu 22.04 we can use system Qt
           if [[ "${{ matrix.image }}" = *"ubuntu-22.04"* ]]; then
             echo "OVERTE_USE_SYSTEM_QT=true" >> $GITHUB_ENV
@@ -170,6 +172,11 @@ jobs:
         submodules: false
         fetch-depth: 1
 
+    - name: Enable ccache
+      uses: hendrikmuhs/ccache-action@v1.2
+      with:
+        key: ${{matrix.os}}-${{matrix.arch}}
+
     - name: Install dependencies
       shell: bash
       if: startsWith(matrix.os, 'Ubuntu') || contains(matrix.os, 'Debian') || startsWith(matrix.os, 'macOS')