Improve CI pipeline

Improve the CI pipeline by doing:

- Run docs build with stable/nightly as required
- Run 32 bit tests (default features with a 32 bit target)
- Run cross tests (default features with a s390x target)

.github/workflows/rust.yml

@@ -17,6 +17,7 @@ jobs:
       - name: Running test script
         env:
           DO_LINT: true
+          DO_DOCS: true
           DO_FEATURE_MATRIX: true
         run: ./contrib/test.sh
 
@@ -45,6 +46,7 @@ jobs:
         uses: dtolnay/rust-toolchain@nightly
       - name: Running test script
         env:
+          DO_DOCSRS: true
           DO_FMT: true
         run: ./contrib/test.sh
 
@@ -100,3 +102,36 @@ jobs:
           RUSTFLAGS: "-C link-arg=-Tlink.x"
           CARGO_TARGET_THUMBV7M_NONE_EABI_RUNNER: "qemu-system-arm -cpu cortex-m3 -machine mps2-an385 -nographic -semihosting-config enable=on,target=native -kernel"
         run: cd embedded/no-allocator && cargo run --target thumbv7m-none-eabi
+
+  Arch32bit:
+    name: Test 32-bit version
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout Crate
+        uses: actions/checkout@v3
+      - name: Checkout Toolchain
+        uses: dtolnay/rust-toolchain@stable
+      - name: Add architecture i386
+        run: sudo dpkg --add-architecture i386
+      - name: Install i686 gcc
+        run: sudo apt-get update -y && sudo apt-get install -y gcc-multilib
+      - name: Install target
+        run: rustup target add i686-unknown-linux-gnu
+      - name: Run tests on i686
+        run: cargo test --target i686-unknown-linux-gnu
+
+  Cross:
+    name: Cross test
+    if: ${{ !github.event.act }}
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout Crate
+        uses: actions/checkout@v3
+      - name: Checkout Toolchain
+        uses: dtolnay/rust-toolchain@stable
+      - name: Install target
+        run: rustup target add s390x-unknown-linux-gnu
+      - name: install cross
+        run: cargo install cross --locked
+      - name: run cross test
+        run: cross test --target s390x-unknown-linux-gnu