Fix a couple of build issues (including CI) (#51)

Author: DavidMazarro

.github/workflows/main.yml

@@ -11,7 +11,8 @@ jobs:
 
     steps:
       - uses: actions/checkout@v2
-      - uses: actions/setup-haskell@v1
+      - name: Setup Haskell
+        uses: haskell/actions/setup@v2
         with:
           ghc-version: ${{ matrix.ghc }}
           cabal-version: 'latest'
@@ -24,7 +25,7 @@ jobs:
             cabal--${{ matrix.ghc }}-
             cabal-
       - run: cabal update
-      - run: cabal configure --enable-tests -fexample
+      - run: cabal configure --enable-tests
       - run: cabal build all --only-dependencies
       - run: cabal build all
       - run: cabal test all