ci(windows): pass --llvm-path to bridge codegen so ffigen finds libclang

.gitea/workflows/build-windows.yml

@@ -13,6 +13,9 @@ on:
 env:
   RUST_VERSION: "1.75"
   LLVM_VERSION: "15.0.6"
+  # Where provision.ps1 installs LLVM. ffigen and flutter_rust_bridge_codegen need
+  # the install root (they append bin\libclang.dll themselves).
+  LLVM_HOME: 'C:\tools\llvm-15.0.6'
   FLUTTER_VERSION: "3.24.5"
   VCPKG_COMMIT_ID: "120deac3062162151622ca4860575a33844ba10b"
   CARGO_EXPAND_VERSION: "1.0.95"
@@ -121,13 +124,27 @@ jobs:
 
       - name: Generate Rust <-> Dart bridge
         shell: bash
+        env:
+          # ffigen searches a hardcoded list of locations for libclang.dll and does
+          # not honor LIBCLANG_PATH; the --llvm-path flag below is what matters.
+          # Setting LIBCLANG_PATH anyway because some other Rust crates (e.g. bindgen)
+          # do read it during the build that follows.
+          LIBCLANG_PATH: '${{ env.LLVM_HOME }}\bin'
         run: |
           # Belt-and-suspenders: also prepend cargo-tools to PATH here, in case
           # GITHUB_PATH propagation from the previous step doesn't take effect.
           export PATH="/c/cargo-tools/bin:$PATH"
           command -v flutter_rust_bridge_codegen || { echo "tool not on PATH; PATH=$PATH"; exit 1; }
+
+          if [ ! -f "${LIBCLANG_PATH}/libclang.dll" ]; then
+            echo "libclang.dll not found at ${LIBCLANG_PATH}"
+            ls "${LIBCLANG_PATH}" || true
+            exit 1
+          fi
+
           pushd flutter && flutter pub get && popd
           flutter_rust_bridge_codegen \
+            --llvm-path "${LLVM_HOME}" \
             --rust-input ./src/flutter_ffi.rs \
             --dart-output ./flutter/lib/generated_bridge.dart \
             --c-output ./flutter/macos/Runner/bridge_generated.h