ci: Add a no_std+alloc check

Author: lu-zero

.github/workflows/wot-td.yml

@@ -79,10 +79,14 @@ jobs:
       uses: dtolnay/rust-toolchain@stable
       with:
         toolchain: stable
+        targets: riscv32imc-unknown-none-elf
 
     - name: Build
       run: cargo build --verbose
 
+    - name: Build (no_std + alloc)
+      run: cargo build --verbose --target riscv32imc-unknown-none-elf --no-default-features --features alloc
+
   docs:
     needs: [reuse, clippy-rustfmt]