configure: Treat win32-clang-g++ the same as win32-g++

This fixes configure with win32-clang-g++ as the native compiler.

Change-Id: Iced43d70b9a0aa413d1f5f6034b42b976cb7c39e
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@qt.io>

configure

@@ -771,7 +771,7 @@ setBootstrapVariable()
         echo "RM_RF = rm -rf" >> "$mkfile"
 
         case `basename "$PLATFORM"` in
-        win32-g++*)
+        win32-*g++*)
             cat "$in_mkfile.win32" >> "$mkfile"
             ;;
         *)