[CRT] Define _NTSYSTEM_ in 2 files to force using import-stubs

This prevents the code from linking to __imp_*, which would pull in the symbol from the import library (e.g. kernel32), which creates problems with the GNU linker, which doesn't like to have the import and a static definition at the same time.

sdk/lib/crt/startup/crt_handler.c

@@ -11,7 +11,7 @@
 #include <memory.h>
 #include <signal.h>
 #include <stdio.h>
-
+#define _NTSYSTEM_
 #include <windef.h>
 #include <winbase.h>