first repair the capatalisation to the Linux path

KSPDIR := ${XDG_DATA_HOME}/Steam/steamapps/common/Kerbal Space Program

then remove some assemblies

-r:Assembly-CSharp,Assembly-CSharp-firstpass,UnityEngine,UnityEngine.UI \

I bodged the version check to always return true just to test it, seems to work okay, but a proper version check and testing will be needed....

the dev branch in jenkins is compiling against 1.6 just fine right now...

which has little to do with the Makefile ?