[PATCH] build: Allow user to specify ruby executable

[David Bremner]

Thomas Schneider <qsx at chaotikum.eu> writes:

> This way, one can build for a different Ruby than $PATH/ruby
> (e. g. different versions, or Ruby in other paths).
>
> Signed-off-by: Thomas Schneider <qsx at chaotikum.eu>

pushed to master.

d