Qt 4.7.0 TP cannot be compiled when qt 4.6.x is installed since qmake is trying to use assistant.prf from Qt 4.6

I'm using Qt 4.6.2 and trying to build Qt 4.7.0 Tech Preview, but getting a linking error like:

x86_64-pc-linux-gnu-g++ Wl,-O1 -Wl,-z,relro -Wl,hash-style=gnu -Wl,as-needed -Wl,sort-common -Wl,as-needed -Wl,-O1 -Wl,-z,relro -Wl,hash-style=gnu -Wl,as-needed -Wl,-sort-common -o ../../bin/qtdemo .obj-release-shared/main.o .obj-release-shared/demoscene.o .obj-release-shared/mainwindow.o .obj-release-shared/demoitem.o .obj-release-shared/score.o .obj-release-shared/demoitemanimation.o .obj-release-shared/itemcircleanimation.o .obj-release-shared/demotextitem.o .obj-release-shared/headingitem.o .obj-release-shared/dockitem.o .obj-release-shared/scanitem.o .obj-release-shared/letteritem.o .obj-release-shared/examplecontent.o .obj-release-shared/menucontent.o .obj-release-shared/guide.o .obj-release-shared/guideline.o .obj-release-shared/guidecircle.o .obj-release-shared/menumanager.o .obj-release-shared/colors.o .obj-release-shared/textbutton.o .obj-release-shared/imageitem.o .obj-release-shared/moc_mainwindow.o .obj-release-shared/moc_demoitemanimation.o .obj-release-shared/moc_menumanager.o .obj-release-shared/qrc_qtdemo.o -L/var/pisi/qt-4.7.0_pre1-78/work/qt-everywhere-opensource-src-4.7.0-tp/lib -L/usr/X11R6/lib -lQtHelp -L/var/pisi/qt-4.7.0_pre1-78/work/qt-everywhere-opensource-src-4.7.0-tp/lib -L/usr/X11R6/lib -lQtAssistantClient -lQtSql -lQtXml -lQtOpenGL -lQtGui -lQtNetwork -lQtCore -lGLU -lGL -lpthread

/usr/bin/ld: cannot find -lQtAssistantClient
collect2: ld returned 1 exit status

After some search I've realized that in qt-everywhere-opensource-src-4.7.0-tp/demos/qtdemo/qtdemo.pro file, first line[1] is:

CONFIG += assistant help x11inc

but there is no assistant.prf file in features directory of 4.7TP[2].

Interesting thing is qmake also looks for .prf files in PREFIX/mkspecs and in DATADIR/mkspecs[3] in addition to mkspecs directory included in the 4.7 tarball. Since my old Qt4.6 installation includes the assistant.prf file and qmake (from Qt4.7tp) tries to use this assistant.prf file from my old Qt4.6 installation, this compilation error occurs. The reason behind this error is line 7 in assistant.prf[4]:

qtAddLibrary(QtAssistantClient)

As far as I understand there is no such library in Qt 4.7 anymore and this is the reason behind the compilation error. As a result, I have removed assistant word from qtdemo.pro file (see the patch attached) and I was able to build 4.7 now.

[1] http://qt.gitorious.org/qt/qt/blobs/4.7/demos/qtdemo/qtdemo.pro#line1
[2] http://qt.gitorious.org/qt/qt/trees/4.7/mkspecs/features
[3] http://qt.gitorious.org/qt/qt/blobs/4.7/qmake/project.cpp#line596
[4] http://qt.gitorious.org/qt/qt/blobs/4.6/mkspecs/features/assistant.prf#line7