fix for win32 - now win32 specific

I now (again) know why it does not work on windows:
it's expanded to -DTOP:FILEPATH=D:/kde/kdesvn/trunk/KDE/kdepimlibs --> cmake splits this after the second ':' and therefore the path is not correct -> ${TOP} is 'D'

CCMAIL: kloecker@kde.org
CCMAIL: neundorf@kde.org

svn path=/trunk/KDE/kdepimlibs/; revision=756119