libqtprofilesetup: Understand $$[QT_INSTALL_LIBS] in .prl files.
libqtprofilesetup: Understand $$[QT_INSTALL_LIBS] in .prl files.

Task-number: QBS-834
Change-Id: Ib9285d5bde64121940989903f22bb12fb3c18309
Reviewed-by: Oswald Buddenhagen <6a8868beda3e139b5ac22b2534a23d3e6ba81819@theqtcompany.com>
Reviewed-by: Jake Petroules <2d627e1cecd5435752fa500bacbe05f7cc90c369@petroules.com>

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