Add #if ASSERTIONS around assert in library_async.js (#20722)

This fixes STRICT + ASYNCIFY + ASSERTIONS=0 builds.

Fixes: #20721

Author: sbc100

src/library_async.js

@@ -156,7 +156,9 @@ addToLibrary({
               } finally {
                 if (!ABORT) {
                   var y = Asyncify.exportCallStack.pop();
+#if ASSERTIONS
                   assert(y === x);
+#endif
 #if ASYNCIFY_DEBUG >= 2
                   dbg(`ASYNCIFY: ${'  '.repeat(Asyncify.exportCallStack.length)} finally ${x}`);
 #endif

test/test_core.py

@@ -8311,6 +8311,7 @@ def test_vswprintf_utf8(self):
   # longjmp or exceptions.
   def test_asyncify_longjmp(self):
     self.set_setting('ASYNCIFY')
+    self.set_setting('STRICT')
     self.do_core_test('test_asyncify_longjmp.c')
 
   # Test that a main with arguments is automatically asyncified.