fix(build): use Homebrew clang for wasm32 C build on macOS (#77)

When CC is set (e.g. ccache cc), the wasm32 C/C++ build can use Apple
Clang, which does not support wasm32-unknown-unknown, so the
datadog-js-zstd WASM build failed. Set CC_wasm32_unknown_unknown and
CXX_wasm32_unknown_unknown to Homebrew's clang so crates like zstd-sys
always use a wasm32-capable compiler.

Add DEVELOPMENT.md with Rust/rustup, macOS LLVM, and yarn setup steps,
and move the build/test notes from README into DEVELOPMENT.md.

Author: watson

DEVELOPMENT.md

@@ -0,0 +1,49 @@
+# Development
+
+## Contributing
+
+See [`CONTRIBUTING.md`](CONTRIBUTING.md).
+
+## Development setup
+
+To build `libdatadog-nodejs` locally (for example, to run tests or try out changes), you need Node.js, Yarn, and Rust.
+
+**Rust (required for native and WASM builds)**
+
+The project compiles Rust for both native Node.js addons and WebAssembly. Use [rustup](https://rustup.rs/) (the recommended and supported method):
+
+1. **Install rustup and Rust** (see https://rustup.rs/ for more options):
+
+   ```bash
+   curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh
+   ```
+
+2. **Ensure Rust is on `PATH`** — the rustup installer prints the command for your shell; run it or open a new terminal.
+
+3. **Add the WebAssembly target** (required for the full build):
+
+   ```bash
+   rustup target add wasm32-unknown-unknown
+   ```
+
+4. **On macOS only** — the WASM build requires LLVM from Homebrew (Apple's Clang has compatibility issues with some crates). Install it before building:
+
+   ```bash
+   brew install llvm
+   ```
+
+5. **Install dependencies:**
+
+   ```bash
+   yarn install
+   ```
+
+## Building
+
+* `yarn build`: Build the default workspaces in debug mode.
+* `yarn build-release`: Build the default workspaces in release mode.
+* `yarn build-all`: Build all workspaces in debug mode. This is useful when working on a workspace that is not a default member yet.
+
+## Run tests
+
+* `yarn test`: Run the JavaScript test suite

README.md

@@ -6,9 +6,3 @@ Node.js bindings for [libdatadog](https://github.com/DataDog/libdatadog).
 
 This project is currently meant to be used only by [dd-trace-js](https://github.com/DataDog/dd-trace-js)
 and installing it directly is not supported at the moment.
-
-## Building
-
-* `yarn build`: Build the default workspaces in debug mode.
-* `yarn build-release`: Build the default workspaces in release mode.
-* `yarn build-all`: Build all workspaces in debug mode. This is useful when working on a workspace that is not a default member yet.

scripts/build-wasm.js

@@ -37,6 +37,11 @@ if (isMacOS) {
     // Add LLVM to PATH if not already included
     env.PATH = `${llvmBinDir}:${env.PATH}`;
   }
+
+  // Force C/C++ code (e.g. zstd-sys) to use Homebrew's clang for wasm32. Otherwise a global
+  // CC (e.g. ccache cc) can point at Apple Clang, which does not support wasm32-unknown-unknown.
+  env.CC_wasm32_unknown_unknown = `${llvmBinDir}/clang`;
+  env.CXX_wasm32_unknown_unknown = `${llvmBinDir}/clang++`;
 }
 
 childProcess.execSync(