Update rust.yml

.github/workflows/rust.yml

@@ -15,6 +15,11 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
+    - uses: actions-rs/toolchain@v1
+      with:
+        toolchain: stable
+        target: armv7-unknown-linux-gnueabihf
+        override: true
     - uses: actions/checkout@v2
     - name: Build
       run: cargo build --verbose