Can't initdb, libdir points to static location

I use PostgreSQL as a default database in our solution and with the
7.2 version I was able to tar up the area pointed to by the --prefix
build argument and untar to an arbitrary path as part of my product
installation and I could initdb the database no problem and get a
running database setup completely.

With the 7.4 released version I get this failure while running initdb:

ERROR:  could not access file "$libdir/ascii_and_mic": No such file or
directory

This is due to the fact that the libdir is pointing to the lib under
the prefix area I specified when I built the postgresql distribution,
but it no longer exists.

I tried modifying initdb to add the -c dynamic_library_path=<mypath>
but that didn't help. It appears that libdir is basically hardcoded to
be PKGLIBDIR from the build, which won't work in this case.

Setting dynamic_library_path=<mypath> in the postgresql.conf would
work I think, except that initdb doesn't use that at creation time.
The datadir has to be empty an initdb time.

Is there an environment variable that can override this like
LD_LIBRARY_PATH ?
I'm looking for any ideas. Thanks.

Tim Farrell