fix hot reloading of property editor with cmake builds

With qmake it was only working if you had insource builds, with cmake there is no option for insource build.

For property development it is essential to have that feature working again.

cmake can set a define where to find the qml files incode, the question is how we enable that feature

• cmake variable
  • but then we can also set a folder inside that variable
• qtcreator process argument with folder variable
• if qml code is right next to the binary then enable that feature (save the relative path to the qml code into the define)

note: in installed snapshots it is even with cmake builds still working, so maybe the path is just wrong in build case