ci: Check at least one C3 target

.github/workflows/build.yml

@@ -34,7 +34,6 @@ jobs:
         run:  cargo xtask --verbose fmt -c
 
   # Compilation check
-  # TODO: check esp32-c3
   check:
     name: check
     runs-on: ubuntu-22.04
@@ -64,6 +63,10 @@ jobs:
           - backend: riscv32-imc-mecall
             platform: hifive1
             rustup-target: riscv32imc-unknown-none-elf
+
+          - backend: riscv-esp32-c3
+            platform: esp32-c3
+            rustup-target: riscv32imc-unknown-none-elf
     steps:
       - name: Checkout
         uses: actions/checkout@v4