Move embind globalThis polyfill to shared code. NFC (#25184)

This will allow us to use it from other places.

Split out from #25172

Author: sbc100

src/lib/libcore.js

@@ -1612,6 +1612,41 @@ addToLibrary({
   emscripten_asm_const_async_on_main_thread: (emAsmAddr, sigPtr, argbuf) => runMainThreadEmAsm(emAsmAddr, sigPtr, argbuf, 0),
 #endif
 
+  $emGlobalThis__internal: true,
+#if SUPPORTS_GLOBALTHIS
+  $emGlobalThis: 'globalThis',
+#else
+  $getGlobalThis__internal: true,
+  $getGlobalThis: () => {
+    if (typeof globalThis != 'undefined') {
+      return globalThis;
+    }
+#if DYNAMIC_EXECUTION
+    return new Function('return this')();
+#else
+    function testGlobal(obj) {
+      // Use __emGlobalThis as a test symbol to see if `obj` is indeed the
+      // global object.
+      obj['__emGlobalThis'] = obj;
+      var success = typeof __emGlobalThis == 'object' && obj['__emGlobalThis'] === obj;
+      delete obj['__emGlobalThis'];
+      return success;
+    }
+    if (typeof self != 'undefined' && testGlobal(self)) {
+      return self; // This works for both "window" and "self" (Web Workers) global objects
+    }
+#if ENVIRONMENT_MAY_BE_NODE
+    if (typeof global != 'undefined' && testGlobal(global)) {
+      return global;
+    }
+#endif
+    abort('unable to get global object.');
+#endif // DYNAMIC_EXECUTION
+  },
+  $emGlobalThis__deps: ['$getGlobalThis'],
+  $emGlobalThis: 'getGlobalThis()',
+#endif // SUPPORTS_GLOBALTHIS
+
 #if !DECLARE_ASM_MODULE_EXPORTS
   // When DECLARE_ASM_MODULE_EXPORTS is not set we export native symbols
   // at runtime rather than statically in JS code.

src/lib/libemval.js

@@ -122,41 +122,6 @@ var LibraryEmVal = {
   _emval_new_u16string__deps: ['$Emval'],
   _emval_new_u16string: (v) => Emval.toHandle(UTF16ToString(v)),
 
-  $emGlobalThis__internal: true,
-#if SUPPORTS_GLOBALTHIS
-  $emGlobalThis: 'globalThis',
-#else
-  $getGlobalThis__internal: true,
-  $getGlobalThis: () => {
-    if (typeof globalThis != 'undefined') {
-      return globalThis;
-    }
-#if DYNAMIC_EXECUTION
-    return new Function('return this')();
-#else
-    function testGlobal(obj) {
-      // Use __emGlobalThis as a test symbol to see if `obj` is indeed the
-      // global object.
-      obj['__emGlobalThis'] = obj;
-      var success = typeof __emGlobalThis == 'object' && obj['__emGlobalThis'] === obj;
-      delete obj['__emGlobalThis'];
-      return success;
-    }
-    if (typeof self != 'undefined' && testGlobal(self)) {
-      return self; // This works for both "window" and "self" (Web Workers) global objects
-    }
-#if ENVIRONMENT_MAY_BE_NODE
-    if (typeof global != 'undefined' && testGlobal(global)) {
-      return global;
-    }
-#endif
-    abort('unable to get global object.');
-#endif // DYNAMIC_EXECUTION
-  },
-  $emGlobalThis__deps: ['$getGlobalThis'],
-  $emGlobalThis: 'getGlobalThis()',
-#endif // SUPPORTS_GLOBALTHIS
-
   _emval_get_global__deps: ['$Emval', '$getStringOrSymbol', '$emGlobalThis'],
   _emval_get_global: (name) => {
     if (!name) {