Merge pull request #14 from msakai/stack-config-set-system-ghc

GitHub Actions: use 'stack config' command for setting system-ghc configuration

.github/workflows/build.yaml

@@ -50,8 +50,8 @@ jobs:
 
       - name: Build
         run: |
+          stack config set system-ghc --global true
           sed -i "s/resolver: .*/resolver: ${{ matrix.resolver }}/" stack.yaml
-          echo "system-ghc: true" >> stack.yaml
           stack build --test --no-run-tests --bench --no-run-benchmarks ${{ matrix.flags }}
 
       - name: Test