Use --sparse option in tar

Author: jneira

.github/workflows/validate.yml

@@ -126,7 +126,7 @@ jobs:
             file $CABAL_EXEC
             $CABAL_EXEC --version
           fi
-          tar -cvf cabal-head.tar -C $(dirname "$CABAL_EXEC") $(basename "$CABAL_EXEC")
+          tar -Scvf cabal-head.tar -C $(dirname "$CABAL_EXEC") $(basename "$CABAL_EXEC")
           echo "CABAL_EXEC_TAR=cabal-head.tar" >> $GITHUB_ENV
 
       # We upload the cabal executable built with the ghc used in the release for: