[CMake] Check if a command exists?

[Alexander Neundorf]

On Monday 03 September 2012, Rui Maciel wrote:
> I have a small project which includes a couple of parsers whose lexers
> are generated by re2c.  I intended to set cmake so that it could check
> if re2c is present in the system, but after browsing through the docs
> I've ended up empty-handed.

Use find_program()

Alex