attempt to cache /nix in Nix Shell Github Action

cachix/install-nix-action#56 (comment)

Author: peterbecich

.github/workflows/haskell-ci.yml renamed to .github/workflows/haskell-ci.yml.temp-disable

@@ -13,6 +13,29 @@ jobs:
     runs-on: ubuntu-latest
     steps:
     - uses: actions/[email protected]
+    # https://github.com/cachix/install-nix-action/issues/56
+    - run: |
+        sudo mkdir -p /nix/store
+        sudo chmod -R 777 /nix
+
+    - name: Cache nix env take N+1
+      uses: actions/[email protected]
+      with:
+        path: |
+          # See https://github.com/actions/cache/pull/726
+          /nix/store/**
+          # Missing something?
+          # /nix/var/nix/*/*
+          # /nix/var/nix/db/*
+          # /nix/var/nix/db/*/**
+          # !/nix/var/nix/daemon-socket/socket
+          # !/nix/var/nix/userpool/*
+          # !/nix/var/nix/gc.lock
+          # !/nix/var/nix/db/big-lock
+          # !/nix/var/nix/db/reserved
+        key: ${{ runner.os }}-nix-store-${{ hashFiles('**') }}
+        restore-keys: ${{ runner.os }}-nix-store-
+
     - uses: cachix/install-nix-action@v16
       with:
         nix_path: nixpkgs=channel:nixos-21.11