I've tracked down my problem with pgxs to Makefile.global in lib/pgxs/src.
These lines seem to be the culprits:
bindir := $(shell pg_config --bindir)
datadir := $(shell pg_config --sharedir)
sysconfdir := $(shell pg_config --sysconfdir)
libdir := $(shell pg_config --libdir)
pkglibdir := $(shell pg_config --pkglibdir)
includedir := $(shell pg_config --includedir)
pkgincludedir := $(shell pg_config --pkgincludedir)
mandir := $(shell pg_config --mandir)
docdir := $(shell pg_config --docdir)
localedir := $(shell pg_config --localedir)
I think it should be running $(pkglibdir)/bin/pg_config
--
Gregory Stark
EnterpriseDB http://www.enterprisedb.com