The autoconf bits are out of date, but the part about `make clang-test`
is still correct, albeit confusing and outdated. This is talking about
clang's regression tests, and there is indeed a `clang-test` target
that's a synonym for the newer but more consistent `check-clang`.
> I'm not really sure what that was supposed to mean, so I won't change
> them myself. But it would actually be better to point at the official
> testing documentation, which is much better nowadays.
I'd say we should reduce this to briefly mention the `check-clang`
target and provide a link to the testing docs. I'm not sure what to do
about the bits about `make VERBOSE=1` and `make VG=1` though - I only
know how to do those by calling lit directly - is there a way to do it
by calling make/ninja anymore?