slh-dsa: ensure no_std compatibility in CI (#876)

Author: tarcieri

.github/workflows/slh-dsa.yml

@@ -17,6 +17,24 @@ env:
   RUSTFLAGS: "-Dwarnings"
 
 jobs:
+  no_std:
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        target:
+          - thumbv7em-none-eabi
+          - wasm32-unknown-unknown
+        rust:
+          - 1.81.0 # MSRV
+          - stable
+    steps:
+      - uses: actions/checkout@v4
+      - uses: dtolnay/rust-toolchain@master
+        with:
+          toolchain: ${{ matrix.rust }}
+          targets: ${{ matrix.target }}
+      - run: cargo build --target ${{ matrix.target }} --no-default-features
+
   test:
     runs-on: ubuntu-latest
     strategy: