Remove timeout slicing from pthread_barrier_wait. NFC (#26847)

In line with commit ee036b7.

Author: kleisauke

system/lib/libc/musl/src/thread/pthread_barrier_wait.c

@@ -87,26 +87,14 @@ int pthread_barrier_wait(pthread_barrier_t *b)
 		while (spins-- && !inst->finished)
 			a_spin();
 		a_inc(&inst->finished);
-#ifdef __EMSCRIPTEN__
-		int is_runtime_thread = emscripten_is_main_runtime_thread();
 		while (inst->finished == 1) {
-			if (is_runtime_thread) {
-				int e;
-				do {
-					// Main runtime thread may need to run proxied calls, so sleep in very small slices to be responsive.
-					e = emscripten_futex_wait(&inst->finished, 1, 1);
-				} while (e == -ETIMEDOUT);
-			} else {
-				// Can wait in one go.
-				emscripten_futex_wait(&inst->finished, 1, INFINITY);
-			}
-		}
+#ifdef __EMSCRIPTEN__
+			emscripten_futex_wait(&inst->finished, 1, INFINITY);
 #else
-		while (inst->finished == 1) {
 			__syscall(SYS_futex,&inst->finished,FUTEX_WAIT|FUTEX_PRIVATE,1,0) != -ENOSYS
 			|| __syscall(SYS_futex,&inst->finished,FUTEX_WAIT,1,0);
-		}
 #endif
+		}
 		return PTHREAD_BARRIER_SERIAL_THREAD;
 	}