With the PGXS boilerplate in place, pg_xlogdump currently fails with an
ominous error message that certain targets cannot be built because
certain files do not exist. Remove that and instead throw a quick error
message alerting the user of the actual problem, which should be easier
to diagnose that the statu quo.
Andres Freund
This program relies on rm_desc backend routines and the xlogreader
infrastructure to emit human-readable rendering of WAL records.
Author: Andres Freund, with many reworks by Álvaro
Reviewed (in a much earlier version) by Peter Eisentraut