[Distutils] How to detect if C compiler installed?

[Frank McIngvale]

Hi, I was wondering if there is a portable
way to determine if a C compiler is available for
compiling extensions. I'm working on a package
that has some extensions that aren't strictly
required, and I'd like to turn on/off building
them based on whether a C compiler is available.

(I know how to do the turn on/off thing, I just
need to know how to check for a C compiler.)

Any hints?
frank