Tweak wasm binding to work with new upstream LLVM backend

lib/binding_web/binding.js

@@ -874,7 +874,10 @@ class Language {
     return bytes
       .then(bytes => loadWebAssemblyModule(bytes, {loadAsync: true}))
       .then(mod => {
-        const functionName = Object.keys(mod).find(key => key.includes("tree_sitter_"));
+        const functionName = Object.keys(mod).find(key =>
+          key.includes("tree_sitter_") &&
+          !key.includes("external_scanner_")
+        );
         const languageAddress = mod[functionName]();
         return new Language(INTERNAL, languageAddress);
       });

script/build-wasm

@@ -62,14 +62,12 @@ done
 
 emcc=
 if which emcc > /dev/null && [[ "$force_docker" == "0" ]]; then
-  export EMCC_FORCE_STDLIBS=libc++
   emcc=emcc
 elif which docker > /dev/null; then
   emcc="docker run               \
     --rm                         \
     -v $(pwd):/src:Z             \
     -u $(id -u)                  \
-    -e EMCC_FORCE_STDLIBS=libc++ \
     trzeci/emscripten-slim       \
     emcc"
 else