ci: add build with stable.

.github/workflows/rust.yml

@@ -12,11 +12,11 @@ env:
 jobs:
   all:
     runs-on: ubuntu-20.04
-    needs: [build, test]
+    needs: [build-nightly, build-stable, test]
     steps:
       - name: Done
         run: exit 0
-  build:
+  build-nightly:
     runs-on: ubuntu-latest
     permissions:
       id-token: write
@@ -41,6 +41,28 @@ jobs:
           chmod +x /usr/local/bin/cargo-batch
           ./ci.sh
           rm -rf target_ci/*{,/release}/{build,deps,.fingerprint}/{lib,}{embassy,stm32}*
+  build-stable:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+        with:
+          submodules: true
+      - name: Cache multiple paths
+        uses: actions/cache@v2
+        with:
+          path: |
+            ~/.cargo/bin/
+            ~/.cargo/registry/index/
+            ~/.cargo/registry/cache/
+            ~/.cargo/git/db/
+            target_ci_stable
+          key: rust-stable-${{ runner.os }}-${{ hashFiles('rust-toolchain.toml') }}
+      - name: build
+        run: |
+          curl -L -o /usr/local/bin/cargo-batch https://github.com/embassy-rs/cargo-batch/releases/download/batch-0.1.0/cargo-batch
+          chmod +x /usr/local/bin/cargo-batch
+          ./ci_stable.sh
+          rm -rf target_ci_stable/*{,/release}/{build,deps,.fingerprint}/{lib,}{embassy,stm32}*
 
   test:
     runs-on: ubuntu-latest