ci: fixes job caches not producing after recent cabal upgrade

Recent cabal adopted XDG guidelines and stores data
across multiple directories under $HOME.
Creating ~/.cabal manually returns old behavior and allows caching single directory again.

.github/workflows/ci.yaml

@@ -262,8 +262,9 @@ jobs:
         run: |
           ghcup install ghc ${{ matrix.ghc }}
           ghcup set ghc ${{ matrix.ghc }}
-      - name: Copy cabal.project
+      - name: Copy cabal.project & fix caching
         run: |
+          mkdir ~/.cabal
           cp cabal.project.non-nix cabal.project
       - name: Cache
         uses: actions/cache@v3