I think der is some weired "package installed by some driver" thing going on. In your mint-emc.txt you write "Install all build depends except libgl1-mesa-dev | libgl1-mesa-swx11-dev:", which was allready installed on my system.
I have an AMD AM1 Athlon x4 5350, maybe this is the problem, dont know.
Had the same error in 17.2 and 17.3 Mate (with and without Codecs)
After installing linuxcnc following your instructions in "mint-emc.txt", linuxcnc starts and runs , but I get an error, which shows up, everytime I do some apt-get stuff in console.
This error is a little bit anoying, but the worst part is, it doesnt allow me to backup my system with remastersys, this error aborts the installation.
I dont know how I get more information to this error, google doesnt help either.
I will run a clean install again, looking at every single package installed, maybe I'll find something.