Blurt out cabal version in both action and build script

.github/workflows/build-macos-package.yml

@@ -9,8 +9,8 @@ jobs:
     strategy:
       matrix:
         os: [macOS-latest]
-        cabal: ["2.4"]
         ghc: ["8.6.5"]
+        cabal: ["2.4"]
 
     steps:
     - uses: actions/checkout@v2
@@ -22,6 +22,10 @@ jobs:
         ghc-version: ${{ matrix.ghc }}
         cabal-version: ${{ matrix.cabal }}
 
+    - name: Check cabal version
+      run: |
+        cabal --version
+
     - name: Install build tools
       run: |
         brew install \