Make RTLD_LOCAL work correctly for preloaded DSOs

Follow-up to commit c9a5e63, for the FS.createPreloadedFile()
case.

Make sure loadWebAssemblyModule() and loadDynamicLibrary()
are called with a valid 'localScope' object when invoked
from the .so file type preload handler.

test/test_core.py

@@ -3960,7 +3960,7 @@ def test_dlfcn_rtld_local(self):
 
   def test_dlfcn_with_preload(self):
     # Create chain of dependencies and load the first libary with preload plugin.
-    # main -> libB.so -> libA.sp
+    # main -> libB.so -> libA.so
     create_file('libA.c', r'''
       #include <stdio.h>
       int libA_fun() {
@@ -3987,7 +3987,7 @@ def test_dlfcn_with_preload(self):
         // Check the file exists in the VFS
         struct stat statbuf;
         assert(stat("/libB.so", &statbuf) == 0);
-        void *lib_handle = dlopen("/libB.so", RTLD_NOW);
+        void *lib_handle = dlopen("/libB.so", RTLD_LOCAL | RTLD_NOW);
         assert(lib_handle);
         typedef int (*intfunc)();
         intfunc x = (intfunc)dlsym(lib_handle, "libB_fun");