ECPG regression tests seem rather fundamentally broken

AFAICT, every buildfarm machine that runs ecpg tests has been failing
since Peter's patch here:
http://archives.postgresql.org/pgsql-committers/2007-01/msg00241.php

Now it looks to me like Peter was simply wrong: we do need to include
libpq because libecpg depends on it. However, I tried reverting the
change and things still did not work. The reason is that the test
programs are built with relative paths to libpq that look like
../../../../../src/interfaces/libpq/libpq.sl.5
and then executed one level up from where they were built, causing
the relative path to be no good. I suspect the only reason it has
been appearing to work for awhile is that people had usable copies
of libpq and perhaps libecpg installed in system-standard library
directories. Take away those preinstalled libs, or render them
version-incompatible, and the ecpg tests stop working.

regards, tom lane