rstrtmgr: Use --prefer-native instead of DLL_WINE_PREATTACH.

dlls/rstrtmgr/Makefile.in

 MODULE    = rstrtmgr.dll
 
-EXTRADLLFLAGS = -mno-cygwin
+EXTRADLLFLAGS = -mno-cygwin -Wb,--prefer-native
 
 C_SRCS = \
 	main.c

dlls/rstrtmgr/main.c

@@ -26,25 +26,6 @@
 
 WINE_DEFAULT_DEBUG_CHANNEL(rstrtmgr);
 
-/*****************************************************
- *      DllMain
- */
-BOOL WINAPI DllMain( HINSTANCE hinst, DWORD reason, LPVOID reserved )
-{
-    TRACE("(%p, %d, %p)\n", hinst, reason, reserved);
-
-    switch(reason)
-    {
-    case DLL_WINE_PREATTACH:
-        return FALSE;  /* prefer native version */
-
-    case DLL_PROCESS_ATTACH:
-        DisableThreadLibraryCalls( hinst );
-        break;
-    }
-    return TRUE;
-}
-
 /***********************************************************************
  * RmGetList (rstrtmgr.@)
  *