gcc: use an absolute path for the precompiled header include
gcc: use an absolute path for the precompiled header include

Task-number: QBS-378

Change-Id: I024ab50578a02e7c48c8488becabdd2fe003d4f6
Reviewed-by: Christian Kandeler <3aa99dcdd3f0cac61fb81c2a11771c0cc2497607@digia.com>

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