default\qmake.conf's QMAKESPEC_ORIGINAL value contains the source directory path, but it should point to the installation path.
This is correct in Qt5beta1 binary package, but wrong in manual build.
E.g. it contains
but Qt is configured with "-prefix C:\WebKitBuildSlave\Qt5.0.0-r38-angle", so it should be
There is also an other problem with this qmake.conf. After the change
WebKit can't resolve the include path. This is necessary for nmake detection.
Also there is an old bug
mkspecs/default/qmake.conf shouldn't use absolute path in the include statement because this will break for Qt binary deployments that cannot patch this file at the installation time, such as internal Symbian SDK deployments that include Qt.
It was just fine as