There are many users working with exactly your environment using qwt.prf like it is. Also qwt.prf doesn't contain any path names it only includes the same files that are used for building qwt.
As you have built Qwt from the command line and fail with building your application with the creator it is obviously a misconfiguration of the creator on your side. I'm pretty sure you can build your applications successfully with qmake/make from the command line with your initial configuration.
Uwe
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