Fix caching of ghcup in perf comparison CI

Author: harendra-kumar

.github/workflows/regression-check.yml

@@ -106,14 +106,20 @@ jobs:
         done
         echo "CI_BENCHMARKS=$CI_BENCHMARKS" >> $GITHUB_ENV
 
+    # Use a sane PATH, especially to pick the right GHC
+    - name: Set PATH to add .local and .ghcup
+      run: echo "$HOME/.local/bin:$HOME/.ghcup/bin:/bin:/usr/bin" > $GITHUB_PATH
+
     - name: Download ghc
       run: |
         if ! ghc --version 2>/dev/null | grep -q "$GHCVER"
         then
           curl -sL -o ./ghcup https://downloads.haskell.org/~ghcup/$GHCUP_VERSION/x86_64-linux-ghcup-$GHCUP_VERSION
           chmod +x ./ghcup
+          export GHCUP_INSTALL_BASE_PREFIX=$HOME
           ./ghcup install ghc $GHCVER
           ./ghcup set ghc $GHCVER
+          ./ghcup install cabal
         fi
         # XXX update only if not present
         cabal update
@@ -147,7 +153,7 @@ jobs:
     - name: Checkout the PR branch
       uses: actions/checkout@v4
       with:
-        # preserve the "charts" directory created by bench-runner
+        # preserve bench-runner and the "charts" directory created by bench-runner
         clean: false
 
     - name: Run benchmarks and append