Only set the FC environment variable

Author: mdpiper

.github/workflows/test.yml

@@ -91,7 +91,7 @@ jobs:
       - name: Configure, build, and install
         working-directory: ${{ github.workspace }}/build
         run: |
-          cmake .. -G Ninja -DCMAKE_Fortran_COMPILER="${{ env.FC }}" -DCMAKE_INSTALL_PREFIX="${{ env.LIBRARY_PREFIX }}" -DCMAKE_BUILD_TYPE=Release
+          cmake .. -G Ninja -DCMAKE_INSTALL_PREFIX="${{ env.LIBRARY_PREFIX }}" -DCMAKE_BUILD_TYPE=Release
           cmake --build . --target install --config Release
 
       - name: Check (for humans)