make dub use my version of dmd

[Steven Schveighoffer]

I'm running into an issue where I need to run an old compiler to build 
something, but the dub installation included with that compiler seems to 
have an infinite loop problem. So I want to run a standalone version of 
dub, but whatever compiler is selected with my path. Problem is, when I 
run the version of dub from the given compiler directory, it looks only 
in that directory for dmd.

OK, I thought, just put it in ~/bin, and run it from there. Doesn't 
work, now it looks in ~/bin (where there is no compiler), and fails.

Is there a way to make dub just use the existing PATH?

-Steve