Link libffi as convenience library

[Tom Tromey]

>>>>> "Anthony" == Anthony Green <green@redhat.com> writes:

>> We were bringing in ffitest.lo from libffi. This resulted in amusing
>> behaviour when the "--main" flag to gcj was omitted, because there was
>> a main() in libgcj itself. This patch builds a libffi convenience
>> library which only contains the proper code, fixing the problem.

Anthony> Why do you think we've never seen this before?

We changed how the libffi objects were found a while back.  Maybe that
change caused it.

Actually, I think ffitest should be in `check_PROGRAMS', not
`noinst_PROGRAMS'.  That way it would only be built by `make check'.
(This wouldn't affect the need for this particular patch though.)

Tom