Re: Mixing CC and a different CLANG seems like a bad idea

I wrote:
> Yeah.  I'm inclined to think we ought to just bite the bullet and fold
> CLANG/CLANGXX into the main list of compiler switch probes, so that we
> check every interesting one four times.

After studying configure's list more closely, that doesn't seem like
a great plan either.  There's a lot of idiosyncrasy in the tests,
such as things that only apply to C or to C++.

More, I think (though this ought to be documented in a comment) that
the policy is to not bother turning on extra -W options in the bitcode
switches, on the grounds that warning once in the main build is enough.
I follow that idea --- but what we missed is that we still need to
turn *off* the warnings we're actively disabling.  I shall go do that,
if no objections.

            regards, tom lane