Add ccache to CI (#375)

.github/workflows/linux.yaml

@@ -51,13 +51,22 @@ jobs:
         shared_lib: [ON, OFF]
 
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
         with:
           fetch-depth: 0
 
+      - name: ccache
+        uses: hendrikmuhs/ccache-action@v1.2
+        with:
+          key: ${{ matrix.os }}-${{ matrix.build_type }}-shared-${{ matrix.shared_lib }}
+
       - name: Configure CMake
         shell: bash
         run: |
+          export CMAKE_CXX_COMPILER_LAUNCHER=ccache
+          export PATH="/usr/lib/ccache:/usr/local/opt/ccache/libexec:$PATH"
+          cmake --version
+
           mkdir build
           cd build
           cmake -D CMAKE_BUILD_TYPE=${{ matrix.build_type }} -D BUILD_SHARED_LIBS=${{ matrix.shared_lib }} -DCMAKE_INSTALL_PREFIX=./install ..
@@ -65,6 +74,8 @@ jobs:
       - name: Build sherpa-onnx for ubuntu
         shell: bash
         run: |
+          export PATH="/usr/lib/ccache:/usr/local/opt/ccache/libexec:$PATH"
+
           cd build
           make -j2
           make install