Exclude AsRef<Path> for no-std builds

And test no-std in CI.

.github/workflows/ci.yml

@@ -44,9 +44,12 @@ jobs:
         run: |
           cargo update -p serde_test --precise 1.0.163
           cargo update -p serde --precise 1.0.69
+      - name: Build
+        run: |
+          cargo build -v --no-default-features
+          cargo build --verbose --features "${{ matrix.features }}"
       - name: Tests
         run: |
-          cargo build --verbose --features "${{ matrix.features }}"
           cargo doc --verbose --features "${{ matrix.features }}" --no-deps
           cargo test --verbose --features "${{ matrix.features }}"
           cargo test --release --verbose --features "${{ matrix.features }}"
@@ -54,6 +57,28 @@ jobs:
         if: matrix.bench != ''
         run: cargo test -v --benches
 
+  nostd:
+    runs-on: ubuntu-latest
+    continue-on-error: false
+    strategy:
+      matrix:
+        include:
+          - rust: stable
+            target: thumbv6m-none-eabi
+            features: zeroize
+
+    name: nostd/${{ matrix.target }}/${{ matrix.rust }}
+    steps:
+      - uses: actions/checkout@v4
+      - uses: dtolnay/rust-toolchain@stable
+        with:
+          toolchain: ${{ matrix.rust }}
+          targets: ${{ matrix.target }}
+      - name: Tests
+        run: |
+          cargo rustc "--target=${{ matrix.target }}" --no-default-features --features "${{ matrix.features }}"
+
+
   miri:
     runs-on: ubuntu-latest
     steps: