Install emsdk for clippy run under wasm32-unknown-unknown target

.github/workflows/ci.yaml

@@ -46,6 +46,12 @@ jobs:
       - name: Checkout repository
         uses: actions/checkout@v2
 
+      - name: Set toolchain versions
+        run: |
+          echo "::set-output name=rust::$(cat rust-toolchain)"
+          echo "::set-output name=emscripten::$(cat emscripten-toolchain)"
+        id: toolchain_versions
+
       - name: Install Rust toolchain
         uses: actions-rs/toolchain@v1
         with:
@@ -61,7 +67,21 @@ jobs:
           ruby-version: ".ruby-version"
           bundler-cache: true
 
-      - uses: Swatinem/rust-cache@v1
+      - name: Cache emsdk
+        uses: actions/cache@v2
+        id: cache
+        with:
+          path: "emsdk-cache"
+          key: emscripten-emsdk-${{ runner.os }}-emsdk-${{ steps.toolchain_versions.outputs.emscripten }}
+
+      - name: Install Emscripten toolchain
+        uses: mymindstorm/setup-emsdk@v10
+        with:
+          version: ${{ steps.toolchain_versions.outputs.emscripten }}
+          actions-cache-folder: "emsdk-cache"
+
+      - name: Verify emcc version
+        run: emcc -v
 
       - name: Check formatting
         run: cargo fmt -- --check --color=auto