simplify language selection in GenericGCC.qbs
simplify language selection in GenericGCC.qbs

Preparation for objcxxFlags.

Change-Id: I8fbe71fa1a26db4fa034cd622a0a9bd0b0ae1998
Reviewed-by: Fawzi Mohamed <7388270c57edd0fabd71d8eb0322d66e3c40e57e@digia.com>
Reviewed-by: Christian Kandeler <3aa99dcdd3f0cac61fb81c2a11771c0cc2497607@digia.com>

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