Cleanup, use GHC_FOR_RELEASE also in validate-old-ghcs

Author: andreasabel

.github/workflows/validate.yml

@@ -218,8 +218,9 @@ jobs:
 
     strategy:
       matrix:
-        ghc: ['9.4.8']
         extra-ghc: ['8.4.4', '8.2.2', '8.0.2']
+          ## GHC 7.10.3 does not install on ubuntu-22.04 with ghcup.
+          ## Older GHCs are not supported by ghcup in the first place.
       fail-fast: false
 
     steps:
@@ -231,32 +232,18 @@ jobs:
           sudo apt-get update
           sudo apt-get install libncurses5 libtinfo5
 
-      # # See https://github.com/haskell/cabal/pull/8739
-      # - name: Sudo chmod to permit ghcup to update its cache
-      #   run: |
-      #     sudo ls -lah /usr/local/.ghcup/cache
-      #     sudo mkdir -p /usr/local/.ghcup/cache
-      #     sudo ls -lah /usr/local/.ghcup/cache
-      #     sudo chown -R $USER /usr/local/.ghcup
-      #     sudo chmod -R 777 /usr/local/.ghcup
-
       - name: Install extra compiler
         run: ghcup install ghc ${{ matrix.extra-ghc }}
 
       - name: GHCup logs
         if: always()
         run: cat /usr/local/.ghcup/logs/*
 
-      # - uses: haskell-actions/setup@v2
-      #   with:
-      #     ghc-version: ${{ matrix.extra-ghc }}
-      #     cabal-version: latest
-      #     cabal-update: false
-
-      - uses: haskell-actions/setup@v2
+      - name: Install primary compiler
+        uses: haskell-actions/setup@v2
         id: setup-haskell
         with:
-          ghc-version: ${{ matrix.ghc }}
+          ghc-version: ${{ env.GHC_FOR_RELEASE }}
           cabal-version: latest
 
       - name: GHC versions
@@ -272,8 +259,8 @@ jobs:
           path: |
             ${{ steps.setup-haskell.outputs.cabal-store }}
             dist-*
-          key: ${{ runner.os }}-${{ matrix.ghc }}-${{ github.sha }}
-          restore-keys: ${{ runner.os }}-${{ matrix.ghc }}-
+          key: ${{ runner.os }}-${{ env.GHC_FOR_RELEASE }}-${{ github.sha }}
+          restore-keys: ${{ runner.os }}-${{ env.GHC_FOR_RELEASE }}-
 
       - name: Validate build
         run: sh validate.sh ${{ env.COMMON_FLAGS }} -s build