[gh-actions] Specify FC env variable during build

.github/workflows/build.yml

@@ -30,7 +30,7 @@ jobs:
         sudo apt-get install
         clang-10
         g++-10
-        gfortran
+        gfortran-10
         hdf5-tools
         libblas-dev
         libboost-dev
@@ -60,7 +60,7 @@ jobs:
     - name: Install homebrew dependencies
       if: matrix.os == 'macos-10.15'
       run: |
-        brew install gcc@10 gfortran llvm boost fftw hdf5 open-mpi openblas
+        brew install gcc@10 llvm boost fftw hdf5 open-mpi openblas
         pip3 install mako numpy scipy mpi4py
         pip3 install -r requirements.txt
 
@@ -79,6 +79,7 @@ jobs:
       env:
         CC: ${{ matrix.cc }}
         CXX: ${{ matrix.cxx }}
+        FC: gfortran-10
         LIBRARY_PATH: /usr/local/opt/llvm/lib
       run: |
         source $HOME/install/share/triqs/triqsvars.sh