The previous coding resulted in contrib modules unintentionally overriding
the use of CONTRIB_TESTDB. There seems no particularly good reason to
allow that (after all, the makefile can set CONTRIB_TESTDB if that's really
what it intends).
In passing, document REGRESS_OPTS where the other pgxs.mk options are
documented.
Back-patch to 9.1 --- in prior versions, there were no cases of contrib
modules setting REGRESS_OPTS without including the --dbname switch, so
while the coding was fragile there was no actual bug.
contrib/xml2 can get by without libxslt; the relevant features just
won't work. But if doesn't have libxml2, or if sepgsql doesn't have
libselinux, the link succeeds but the module then fails to work at load
time. To avoid that, link the require libraries unconditionally, so
that it will be clear at link-time that there is a problem.
Per discussion with Tom Lane and KaiGai Kohei.
This is still pretty rough - among other things, the documentation
needs work, and the messages need a visit from the style police -
but this gets the basic framework in place.
KaiGai Kohei
