Per Issue #7 from armanddp, it seems the RHEL/CentOS packages of Postgres are built against libpam, which shows up in the LIBS reported by pg_config. We don't actually need to link in libpam for pg_repack, so manually remove it from our LIBS. This helps a little bit for building on RHEL/CentOS, though the issue of libpgport.a missing on that platform still looms.