Avoid PGXS=1 by only building as an extension
Avoid PGXS=1 by only building as an extension

This is probably not going to get into contrib anytime soon, so
un-crib that bit of Makefile.

Signed-off-by: Daniel Farina <3d0f3b9ddcacec30c4008c5e030e6c13a478cb4f@heroku.com>

logplex/pg_logfebe,logplex/pg_logfebe