fix(wasm): pass target triple to clang (#5385)

Problem: The `clang` binary contained in the WASI-SDK releases downloaded from Github does not work on all platforms (e.g., Alpine/MUSL), but a custom (LLVM) `clang` built for the platform will default to that target, making it impossible to build wasm parsers.

Solution: Always pass `wasm32` target triple when calling clang to compile to wasm.

Notes:
* This assumes the custom `clang` is (installed or linked) to `$TREE_SITTER_WASI_SDK_PATH/bin`.
* This requires a full LLVM clang; Apple clang does not support `wasm` targets. 
* Tree-sitter expects a specified version of WASI-SDK, including a specific `clang` version. Other versions may but are not guaranteed to work.

crates/loader/src/loader.rs

@@ -1388,6 +1388,7 @@ impl Loader {
 
         let mut compile_command = Command::new(&clang_exe);
         compile_command.current_dir(src_path).args([
+            "--target=wasm32-unknown-wasi",
             "-o",
             output_path,
             "-fPIC",