question about setup.py and CC and LDSHARED env variables on Solaris

[srf99 at ferg.org]

Recently I was trying to compile/install cx_Oracle on our Solaris
system.

When I ran "python setup.py build" I got the following message:
"/usr/ucb/cc: language optional software package not installed"

I Googled around and discovered that this is a frequently-encountered
issue on Solaris systems, because Solaris systems don't have the
Solaris C compiler installed by default.  (We certainly don't.  We
use  gcc instead.)

After poking around in the source code for distutils, I figured out
that I could get setup.py to work if -- *before* running setup.py -- I
set two environment variables:

    export CC=gcc
    export LDSHARED="gcc -G"

Afterward, in searching the Web, I couldn't find any documentation to
tell me that I had to do this, or why, or when.

So my question is:
Does anyone know the location of documentation (about distutils, or
about using setup.py) that tells you

 - that you have to do this,
 - why you have to do it,
 - the circumstances under which you have to do it?

I'm a Unix newbie, so I may very well have missed something obvious.

Thanks in advance,
-- Steve Ferg