Use prebuilt protoc

.github/workflows/ci.yml

@@ -15,27 +15,13 @@ jobs:
     steps:
     - name: Check out code
       uses: actions/checkout@v2
-    - name: Cache protobuf library
-      if: matrix.protobuf_lib == 'protobuf-cpp'
-      id: cache-protobuf
-      uses: actions/cache@v1
-      with:
-        path: protobuf-25.1
-        key: ${{ runner.os }}-protobuf-25.1
-    - name: Build protobuf library
-      if: matrix.protobuf_lib == 'protobuf-cpp' && steps.cache-protobuf.outputs.cache-hit != 'true'
-      run: |
-        wget https://github.com/protocolbuffers/protobuf/releases/download/v25.1/protobuf-25.1.tar.gz
-        tar -xf protobuf-25.1.tar.gz
-        cd protobuf-25.1
-        ./configure
-        make
     - name: Install protobuf library
       if: matrix.protobuf_lib == 'protobuf-cpp'
       run: |
-        cd protobuf-25.1
-        sudo make install
-        sudo ldconfig
+        wget https://github.com/protocolbuffers/protobuf/releases/download/v25.1/protoc-25.1-linux-x86_64.zip
+        unzip protoc-25.1-linux-x86_64.zip -d protoc-25.1
+        cp protoc-25.1/bin/* /usr/local/bin/
+        cp protoc-25.1/include/* /usr/local/include/
     - name: Install Valgrind
       if: matrix.valgrind == 'valgrind'
       run: sudo apt update && sudo apt install -y valgrind