I think it's ok to do `grep ruby` instead of `grep ruby-2`, although I put `-2` to ensure it is ruby version 2.x, iirc, it might not work with older versions.
By removing:
``` -ifeq ($(RUBYVER),) -RUBYVER=ruby-2.3 -endif ```
Another test has to be done to be sure RUBYVER is not empty. I looked a bit more into the Makefile, and I think that the order of doing the detection should be changed. I will push a commit very soon to fix all.