I’ve installed rvm + ruby systemwide.

which ruby
/usr/local/rvm/rubies/ruby-2.1.1/bin/ruby

and:

/usr/bin/env: ruby: No such file or directory

Everything else works fine, putting direct path of ruby in my executables work fine.

The PATH is what the env program uses to search for your executables. You can change this per-user (in the $HOME/.bashrc). In order to do that, run nano $HOME/.bashrc and go to the last line, add a new line

export PATH=$PATH:/usr/local/rvm/rubies/ruby-2.1.1/bin

To change it at a system level you sudo nano /etc/login.defs and change this line

ENV_PATH        PATH=/usr/local/bin:/usr/bin:/bin:/usr/local/games:/usr/games

to :

ENV_PATH        PATH=/usr/local/bin:/usr/bin:/bin:/usr/local/games:/usr/games:/usr/local/rvm/rubies/ruby-2.1.1/bin

If you set your $PATH var to use the wrapper directory associated with the Ruby version you want to use e.g.