Fix for starting pthreads when -sENVIRONMENT=worker (#21993)

Fixes: #21989

Author: sbc100

src/library_pthread.js

@@ -429,7 +429,7 @@ var LibraryPThread = {
         // a pthread.
         'workerData': 'em-pthread',
 #endif
-#if ENVIRONMENT_MAY_BE_WEB
+#if ENVIRONMENT_MAY_BE_WEB || ENVIRONMENT_MAY_BE_WORKER
         // This is the way that we signal to the Web Worker that it is hosting
         // a pthread.
         'name': 'em-pthread',

test/test_browser.py

@@ -4868,11 +4868,15 @@ def test_single_file_worker_js(self):
 
   # Tests that pthreads code works as intended in a Worker. That is, a pthreads-using
   # program can run either on the main thread (normal tests) or when we start it in
-  # a Worker in this test (in that case, both the main application thread and the worker threads
-  # are all inside Web Workers).
-  def test_pthreads_started_in_worker(self):
+  # a Worker in this test (in that case, both the main application thread and the worker
+  # threads are all inside Web Workers).
+  @parameterized({
+    '': ([],),
+    'limited_env': (['-sENVIRONMENT=worker'],),
+  })
+  def test_pthreads_started_in_worker(self, args):
     self.set_setting('EXIT_RUNTIME')
-    self.compile_btest('pthread/test_pthread_atomics.cpp', ['-o', 'test.js', '-pthread', '-sPTHREAD_POOL_SIZE=8'], reporting=Reporting.JS_ONLY)
+    self.compile_btest('pthread/test_pthread_atomics.cpp', ['-o', 'test.js', '-pthread', '-sPTHREAD_POOL_SIZE=8'] + args, reporting=Reporting.JS_ONLY)
     create_file('test.html', '''
       <script>
         new Worker('test.js');