There is at least one case in configure where it exist with a code of 0
but does not create .qmake.cache. Detect this and avoid continuing.
Change-Id: I0554991e5d4a50b7072494c080fa2c593e03b726
Reviewed-on: http://codereview.qt-project.org/6094
Reviewed-by: Qt Sanity Bot <qt_sanity_bot@ovi.com>
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@nokia.com>