Add ~/.rustup to the list of cached paths

And restore skipping of rust install if it hasn't changed.

.github/workflows/ci.yml

@@ -32,11 +32,12 @@ jobs:
           path: |
             ~/.cargo/registry
             ~/.cargo/git
+            ~/.rustup
             target
           key: ${{ runner.os }}-cargo-${{ hashFiles('Cargo.lock') }}
 
       - name: Install Rust
-        # if: steps.cache.outputs.cache-hit != 'true'
+        if: steps.cache.outputs.cache-hit != 'true'
         uses: actions-rs/toolchain@v1
         with:
           toolchain: stable