Makefile RUN_DEPENDS= option

[Ernie Luzar]

Have a simple port that needs wget to work.

I want RUN_DEPENDS to first check if wget is already installed, IE: is 
the running executable in the search path whether installed as a 
compiled port or installed as a package and if so bypass any more wget 
processing. If running executable not found then to auto install using 
pkg version and if not found there to do port compile method.

How would I code that?