libqtprofilesetup: Turn "-pthread" into "-lpthread"
libqtprofilesetup: Turn "-pthread" into "-lpthread"

Otherwise we get errors, because we interpret generic options as linker
flags, but -pthread is a driver option.
Add a warning for all other "raw" options encountered on the right-hand
side of QMAKE_PRL_LIBS, as those are not expected there.

Change-Id: If4555caff886c691bddf3ee17bbe7490f9b8fc12
Reviewed-by: Joerg Bornemann <47777b9406dbddd02a3fdca8341789a013805a11@qt.io>

qtproject/qt-labs-qbs,qt-labs/qbs,qtproject/qt-labs-qbs,qt-labs/qbs,qtproject/qt-labs-qbs,qt-labs/qbs,qt-labs/qbs,qtproject/qt-labs-qbs,qt-labs/qbs,qt-labs/qbs,qtproject/qt-labs-qbs,qtproject/qt-labs-qbs,qt-labs/qbs,qtproject/qt-labs-qbs