Use modern CMake features in plugin build macro.
Use modern CMake features in plugin build macro.

This allows external projects to use modern CMake features together
with CTK plug-ins being build with this macro.

msmolens/CTK,mehrtash/CTK,CJGoch/CTK,commontk/CTK,danielknorr/CTK,laurennlam/CTK,danielknorr/CTK,jcfr/CTK,SINTEFMedtek/CTK,naucoin/CTK,naucoin/CTK,jcfr/CTK,151706061/CTK,SINTEFMedtek/CTK,AndreasFetzer/CTK,sankhesh/CTK,rkhlebnikov/CTK,Heather/CTK,AndreasFetzer/CTK,jcfr/CTK,rkhlebnikov/CTK,mehrtash/CTK,laurennlam/CTK,SINTEFMedtek/CTK,rkhlebnikov/CTK,fedorov/CTK,msmolens/CTK,SINTEFMedtek/CTK,laurennlam/CTK,CJGoch/CTK,sankhesh/CTK,CJGoch/CTK,fedorov/CTK,sankhesh/CTK,SINTEFMedtek/CTK,commontk/CTK,AndreasFetzer/CTK,laurennlam/CTK,CJGoch/CTK,151706061/CTK,sankhesh/CTK,ddao/CTK,fedorov/CTK,ddao/CTK,Heather/CTK,151706061/CTK,fedorov/CTK,rkhlebnikov/CTK,Sardge/CTK,Sardge/CTK,commontk/CTK,naucoin/CTK,151706061/CTK,naucoin/CTK,CJGoch/CTK,danielknorr/CTK,Heather/CTK,ddao/CTK,Heather/CTK,danielknorr/CTK,ddao/CTK,Sardge/CTK,commontk/CTK,Sardge/CTK,msmolens/CTK,jcfr/CTK,mehrtash/CTK,jcfr/CTK,mehrtash/CTK,msmolens/CTK,151706061/CTK,AndreasFetzer/CTK