Qmake should not rebuild all the code in QtCore, but currently it does.
When linking against QtCore, all the symbols get duplicated. A clever
linker will "deduplicate" the symbols again, so this actually works
with shared Qt builds, but it fails for static builds.
Do not rely on the linker being clever and just do not link Qt at all
for qmake.
Change-Id: I0f79ed9176a19ee884dd425e5f23c26cf69dc422
Reviewed-by: Tobias Hunger <tobias.hunger@qt.io>
a1752276e0