Fix for clang-10 toolchain

.github/workflows/test-compile.yml

@@ -74,6 +74,7 @@ jobs:
         uses: aminya/setup-cpp@v1
         with:
           compiler: ${{ matrix.compiler }}
+          gcc: ${{ (matrix.os == 'ubuntu-latest' && matrix.compiler == 'clang-10') && '10' || '' }}
 
       - name: Tool versions
         shell: bash
@@ -81,6 +82,11 @@ jobs:
           $CC --version
           $CXX --version
 
+      - name: Fix clang-10 toolchain
+        if: matrix.os == 'ubuntu-latest' && matrix.compiler == 'clang-10'
+        run: |
+          echo "CXXFLAGS=--gcc-toolchain=/usr/lib/gcc/x86_64-linux-gnu/10 -stdlib=libstdc++" >> $GITHUB_ENV
+
       # minimum standard
       - name: Build C++20
         shell: bash