Fix pthread compatibility on Deno

`importScripts()` is always `undefined` on Deno.

src/library_pthread_stub.js

@@ -18,7 +18,7 @@ var LibraryPThreadStub = {
 
   emscripten_is_main_browser_thread: () =>
 #if MINIMAL_RUNTIME
-    typeof importScripts == 'undefined'
+    typeof WorkerGlobalScope == 'undefined'
 #else
     !ENVIRONMENT_IS_WORKER
 #endif

src/runtime_pthread.js

@@ -31,14 +31,9 @@ if (ENVIRONMENT_IS_PTHREAD) {
 
     Object.assign(globalThis, {
       self: global,
-      // Dummy importScripts.  The presence of this global is used
-      // to detect that we are running on a Worker.
-      // TODO(sbc): Find another way?
-      importScripts: () => {
-#if ASSERTIONS
-        assert(false, 'dummy importScripts called');
-#endif
-      },
+      // The presence of this global is used to detect
+      // that we are running on a Worker.
+      WorkerGlobalScope: global,
       postMessage: (msg) => parentPort.postMessage(msg),
     });
   }

src/shell.js

@@ -84,7 +84,7 @@ var ENVIRONMENT_IS_AUDIO_WORKLET = typeof AudioWorkletGlobalScope !== 'undefined
 var ENVIRONMENT_IS_WEB = {{{ ENVIRONMENT === 'web' }}};
 #if PTHREADS && ENVIRONMENT_MAY_BE_NODE
 // node+pthreads always supports workers; detect which we are at runtime
-var ENVIRONMENT_IS_WORKER = typeof importScripts == 'function';
+var ENVIRONMENT_IS_WORKER = typeof WorkerGlobalScope != 'undefined';
 #else
 var ENVIRONMENT_IS_WORKER = {{{ ENVIRONMENT === 'worker' }}};
 #endif
@@ -96,7 +96,7 @@ var ENVIRONMENT_IS_SHELL = {{{ ENVIRONMENT === 'shell' }}};
 #else // ENVIRONMENT
 // Attempt to auto-detect the environment
 var ENVIRONMENT_IS_WEB = typeof window == 'object';
-var ENVIRONMENT_IS_WORKER = typeof importScripts == 'function';
+var ENVIRONMENT_IS_WORKER = typeof WorkerGlobalScope != 'undefined';
 // N.b. Electron.js environment is simultaneously a NODE-environment, but
 // also a web environment.
 var ENVIRONMENT_IS_NODE = typeof process == 'object' && typeof process.versions == 'object' && typeof process.versions.node == 'string' && process.type != 'renderer';
@@ -337,7 +337,7 @@ if (ENVIRONMENT_IS_DENO) { // Deno
 if (ENVIRONMENT_IS_SHELL) {
 
 #if ENVIRONMENT && ASSERTIONS
-  if ((typeof process == 'object' && typeof require === 'function') || typeof window == 'object' || typeof importScripts == 'function') throw new Error('not compiled for this environment (did you build to HTML and try to run it not on the web, or set ENVIRONMENT to something - like node - and run it someplace else - like on the web?)');
+  if ((typeof process == 'object' && typeof require === 'function') || typeof window == 'object' || typeof WorkerGlobalScope != 'undefined') throw new Error('not compiled for this environment (did you build to HTML and try to run it not on the web, or set ENVIRONMENT to something - like node - and run it someplace else - like on the web?)');
 #endif
 
 #if ENVIRONMENT_MAY_BE_SHELL
@@ -423,7 +423,7 @@ if (ENVIRONMENT_IS_WEB || ENVIRONMENT_IS_WORKER) {
   }
 
 #if ENVIRONMENT && ASSERTIONS
-  if (!(typeof window == 'object' || typeof importScripts == 'function')) throw new Error('not compiled for this environment (did you build to HTML and try to run it not on the web, or set ENVIRONMENT to something - like node - and run it someplace else - like on the web?)');
+  if (!(typeof window == 'object' || typeof WorkerGlobalScope != 'undefined')) throw new Error('not compiled for this environment (did you build to HTML and try to run it not on the web, or set ENVIRONMENT to something - like node - and run it someplace else - like on the web?)');
 #endif
 
 #if PTHREADS && ENVIRONMENT_MAY_BE_NODE

src/shell_minimal.js

@@ -137,7 +137,7 @@ function ready() {
 #if PTHREADS
 // MINIMAL_RUNTIME does not support --proxy-to-worker option, so Worker and Pthread environments
 // coincide.
-var ENVIRONMENT_IS_WORKER = typeof importScripts == 'function';
+var ENVIRONMENT_IS_WORKER = typeof WorkerGlobalScope != 'undefined';
 var ENVIRONMENT_IS_PTHREAD = ENVIRONMENT_IS_WORKER && self.name?.startsWith('em-pthread');
 
 #if ENVIRONMENT_MAY_BE_NODE