The Xcode generator creates a makefile for running 'make qmake', and the
makefile passes -o to ensure it writes to the same Xcode project. This
fails when qmake then treats -o foo.xcodeproj/project.xcproj as not only
setting the output filename, but also the output directory to foo.xcodeproj,
which results in the Xcode project trying to reference files relative
to this directory, such as '../main.cpp'.
Unfortunatly the output filename parsing happens too early for us to know
whether or not the generator is Xcode, so we just have to assume that
a certain combination of output filename and directories means we are
generating an Xcode project.
Change-Id: I0901d4db995f287c35cbbbd015683d5abda6d0f5
Reviewed-by: Richard Moe Gustavsen <richard.gustavsen@digia.com>