Use Swatinem/rust-cache@v2 for caching on Github CI

Author: hrxi

.github/workflows/build.yaml

@@ -14,14 +14,7 @@ jobs:
           - nightly
     steps:
       - uses: actions/checkout@v2
-      - uses: actions/cache@v2
-        if: ${{ matrix.rust == 'stable' }}
-        with:
-          path: |
-            ~/.cargo/registry
-            ~/.cargo/git
-            target
-          key: ${{ runner.os }}-cargo-${{ hashFiles('**/Cargo.lock') }}
+      - uses: Swatinem/rust-cache@v2
       - uses: actions-rs/toolchain@v1
         with:
           profile: minimal