Setup cache for cargo

.github/workflows/rust.yml

@@ -17,7 +17,14 @@ jobs:
     steps:
     - uses: actions/checkout@v2
       with:
-        submodules: true 
+        submodules: true
+    - uses: actions/cache@v2
+      with:
+        path: |
+          ~/.cargo/registry
+          ~/.cargo/git
+          target
+        key: ${{ runner.os }}-cargo-${{ hashFiles('**/Cargo.lock') }}
     - name: Install intel compute runtime
       run: |
         sudo add-apt-repository ppa:intel-opencl/intel-opencl