ci: Use github action's cache in addition to sccache (#4417)

.github/workflows/ci.yml

@@ -52,6 +52,23 @@ jobs:
           mkdir -p target/release
           tar --exclude=".git*" --exclude=target --exclude=deno_typescript/typescript/tests --exclude=third_party/cpplint --exclude=third_party/node_modules --exclude=third_party/python_packages --exclude=third_party/prebuilt -czvf target/release/deno_src.tar.gz -C .. deno
 
+      # Cache https://github.com/actions/cache/blob/master/examples.md#rust---cargo
+      - name: Cache cargo registry
+        uses: actions/cache@v1
+        with:
+          path: ~/.cargo/registry
+          key: ${{ runner.os }}-cargo-registry-${{ hashFiles('**/Cargo.lock') }}
+      - name: Cache cargo index
+        uses: actions/cache@v1
+        with:
+          path: ~/.cargo/git
+          key: ${{ runner.os }}-cargo-index-${{ hashFiles('**/Cargo.lock') }}
+      - name: Cache cargo build
+        uses: actions/cache@v1
+        with:
+          path: target
+          key: ${{ runner.os }}-cargo-build-target-${{ hashFiles('**/Cargo.lock') }}
+
       - name: Install rust
         uses: hecrj/setup-rust-action@v1
         with:
@@ -134,10 +151,16 @@ jobs:
         if: matrix.kind == 'lint'
         run: python ./tools/test_format.py
 
-      - name: Build
+      - name: Build release
         if: matrix.kind == 'test_release' || matrix.kind == 'bench'
         run: cargo build --release --locked --all-targets
 
+      - name: Build debug
+        if: matrix.kind == 'test_debug'
+        run: |
+          echo ::set-env name=DENO_BUILD_MODE::debug
+          cargo build --locked --all-targets
+
       - name: Test release
         if: matrix.kind == 'test_release'
         run: cargo test --release --locked --all-targets