Use gcc-11 for build-ubuntu-static-libs

.github/workflows/c-cpp.yml

@@ -56,8 +56,10 @@ jobs:
     steps:
     - name: Install dependencies
       run: |
+        sudo add-apt-repository -y ppa:ubuntu-toolchain-r/test
         sudo apt update
-        sudo apt install -y git build-essential cmake autoconf libgss-dev
+        sudo apt install -y git build-essential cmake autoconf libgss-dev gcc-11 g++-11
+        sudo update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-11 100 --slave /usr/bin/g++ g++ /usr/bin/g++-11 --slave /usr/bin/gcov gcov /usr/bin/gcov-11
 
     - name: Checkout repository
       uses: actions/checkout@v2