qmake automatically appends the library's major version number to the
DLL file name on Windows, as DLL naming doesn't include the version
number on a suffix like on Unix systems.
This flag makes it so qmake skips adding. This will allow us to insert
Qt's major version number at a different position.
Change-Id: I25d471038841fb0c5a34ef6b3bd6266aa33cebd1
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@digia.com>