ocaml/opam — pull request #1061 by vbmithr (2014-01-06 14:42:59+00:00)
Title: Do not use which anymore.

`which` is an issue even on some Linux distributions, for example NixOS.
See this thread:
http://stackoverflow.com/questions/592620/how-to-check-if-a-program-exists-from-a-bash-script