Commit 4bb004de94 broke the linker
options in generated Visual Studio projects.
We need to call fixLibFlags on QMAKE_LIBS and QMAKE_LIBS_PRIVATE.
Task-number: QTBUG-48936
Change-Id: I2f12bf0117d27104cd34f2f43fdeb7b948fa375e
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@theqtcompany.com>