QmakeParser: Fix tests compilation
QmakeParser: Fix tests compilation

locker only exists with PROPARSER_THREAD_SAFE defined.

Broken by dedcd25924743e494055c1e0195aeef0f3983a1d

Change-Id: Ieee60dc6f567ab1c3a59697a1760afb2990496f6
Reviewed-by: Oswald Buddenhagen <6a8868beda3e139b5ac22b2534a23d3e6ba81819@theqtcompany.com>

xianian/qt-creator,xianian/qt-creator,xianian/qt-creator,martyone/sailfish-qtcreator,martyone/sailfish-qtcreator,martyone/sailfish-qtcreator,xianian/qt-creator,xianian/qt-creator,xianian/qt-creator,martyone/sailfish-qtcreator,martyone/sailfish-qtcreator,martyone/sailfish-qtcreator,xianian/qt-creator,xianian/qt-creator,martyone/sailfish-qtcreator,xianian/qt-creator,martyone/sailfish-qtcreator,martyone/sailfish-qtcreator