Fix main() signature of headersclean stub file

Fix MinGW build errors by using the standard main signature.

Change-Id: I0ebe7307a825a7ec50e654f163fbf8fe7060a478
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@digia.com>

mkspecs/features/data/headersclean/tst_headersclean.cpp.in

@@ -48,7 +48,7 @@
 $${includes}
 #include <QtCore/qglobal.h>
 
-int main()
+int main(int, char **)
 {
     qWarning(\"This is a compile test only\");
     return 0;