fix build with MinGW header version > 3.0

Commit 7dffc4f4

 broke the compilation with MinGW64 3.1 and above.
The work-around for mingw-w64 bug #464 must only applied to
MinGW versions that are affected.

Task-number: QTBUG-46712
Change-Id: I62bda4db361d15849fa071d0acaee72254d34bd6
Reviewed-by: Oliver Wolff <oliver.wolff@theqtcompany.com>