qbs_benchmarker: Fix interpretation of massif output
qbs_benchmarker: Fix interpretation of massif output

We mistakenly read the "extra" value rather than the "total" one.

Change-Id: I06e584ffffb535687d72111ca7a884c94dac2878
Reviewed-by: Joerg Bornemann <47777b9406dbddd02a3fdca8341789a013805a11@qt.io>

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