Moc'ing XXXX.h... File not found / no such file

There's a couple potential causes for having issue with Moc'ing (QT) files in Visual Studio 201X.

For the most part, the fact that you get this message means that QT plugin is working, so I won't go into trouble-shooting that.

In my case, it had to do with the QTDIR environment variable being 'cached' in the vcproj.user file.

In otherwords, I set my system env QTDIR=c:\qt, and later changed it to c:\qt5

VS continues to use c:\qt due to the vcproj.user file

Stupid VS >:I