Compiler for testing a bootstrapped glibc?

[Brooks Moses <bmoses at google dot com>]

Glibc folks -

I've run into a conundrum with testing our bootstrapped-from-scratch
glibc builds, and I'm curious how other people's processes work.

Recently, we updated to a version of glibc that can do a single-step
bootstrap -- and so we now build a static-only GCC with no glibc, and
then build glibc using that GCC.  This works great -- but then we want
to run "make check".  And, unfortunately, glibc's testsuite requires
more than just a static-only GCC.

There are a couple of solution directions that I've thought of:

1) Build a dynamic GCC using the just-built glibc, and install it on
top of the static-only GCC we used for building.  This is arguably
simpler, but means rebuilding anything in glibc after testing will get
different results than before testing.  It also increases the overall
build-and-test time.

2) Test the glibc with a different (pre-existing) compiler instead of
with the compiler we used to build it.  This is what I'd prefer, but I
couldn't figure out how to do that without doing evil sed things to
the generated makefile fragments.

Is there a good way to test against a different compiler than the
build compiler?  Or is there a good alternative here that I'm missing?
 How do other people handle this?

Thanks,
- Brooks