Skip eintr.t on FreeBSD (see perl #85842 and #84688).

Skip eintr.t on FreeBSD (see perl #85842 and #84688).

It appears that a larger PerlIO buffer combined with writing to a
pipe triggers an alternate write mechanism in FreeBSD called a
direct write, which is not interruptible by signals.  That's
somewhat speculative and has not been confirmed by someone with
knowledge of FreeBSD internals, but we do know the test hangs, so
it's best not to run it for now.