Add tests for using the toolchain installed by hyperlight_guest_bin

LGTM.

Your comment about not seeing failures with clang.exe made me realise that I'm not sure if we actually have any tests in core hyperlight that make sure this toolchain works to build something; we used to use it to build WAMR when we were experimenting with that, but I don't think we have anything using it right now. It would be nice to add a test guest that actually builds libz or openssl or something with it, though. I don't know if it makes sense to that as part of this PR, but maybe add an issue for it if not?

_Originally posted by @syntactically in https://github.com/hyperlight-dev/hyperlight/pull/572#pullrequestreview-2961733870_