Ok. Thanks for sharing that.
I now have set up the variable only for the root of the devkit and changed all the references in to the libraries in the template like:
$(AC_DEVKIT)/Support/Modules/...
This variable can be changed using a userMacro in a custom property sheet. So now only one variable to control. I don't have to target various versions of the devkit at the moment, so this setup works for me