pem2mincrypt doesn't build on Ubuntu
Line #12 is now this: gcc $(LDFLAGS) -o $(EXE) $(OBJ)
In order for Ubuntu to build it, it needs to be this: gcc -o $(EXE) $(OBJ) $(LDFLAGS)
His is just a sample Makefile, it is not meant to be portable, so you have to tweak it for your environment. What versions of Ubuntu and gcc are you using?
Linux builduntuvm 3.16.0-34-generic #47-Ubuntu SMP Fri Apr 10 18:02:58 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux gcc (Ubuntu 4.9.1-16ubuntu6) 4.9.1
I also tried it on a bone-stock Ubuntu 14.04 64-bit workstation. (Same result).
So, I guess what I'm saying is, if you just change that line in the Makefile, it'll work for everyone. :-)
Maybe not quite for every one, but most people :) Please open a PR and I'll merge it.