Fix for -pthread + -sRELOCATABLE (#22110)

Fixes: #22108

Author: sbc100

src/library_pthread.js

@@ -1242,6 +1242,12 @@ var LibraryPThread = {
       }
     }
   },
+#elif RELOCATABLE
+  // Provide a dummy version of _emscripten_thread_exit_joinable when
+  // RELOCATABLE is used without MAIN_MODULE.  This is because the call
+  // site in pthread_create.c is not able to distinguish between these
+  // two cases.
+  _emscripten_thread_exit_joinable: (thread) => {},
 #endif // MAIN_MODULE
 
   $checkMailbox__deps: ['$callUserCallback',

test/test_other.py

@@ -11922,6 +11922,10 @@ def test_pthread_reuse(self):
     self.set_setting('PTHREAD_POOL_SIZE', 1)
     self.do_run_in_out_file_test('other/test_pthread_reuse.c')
 
+  @node_pthreads
+  def test_pthread_relocatable(self):
+    self.do_runf('hello_world.c', 'hello, world!', emcc_args=['-sRELOCATABLE'])
+
   def test_stdin_preprocess(self):
     create_file('temp.h', '#include <string>')
     outputStdin = self.run_process([EMCC, '-x', 'c++', '-dM', '-E', '-'], input="#include <string>", stdout=PIPE).stdout