How to use plpgsql on AIX

When I tried it to install on AIX it said:
gmake install
gmake -C src install
gmake[1]: Entering directory
`/home/netvisor/postgresql-6.4.2/src/pl/plpgsql/src'
plpgsql not installed due to lack of shared library support.
gmake[1]: Leaving directory
`/home/netvisor/postgresql-6.4.2/src/pl/plpgsql/src'

What can I do now?

            Thanks in advance for your reply

--------------------------------------------------------------------------------
Sebestyén Zoltán <szoli@netvisor.hu>    I'm believing that the Holy Spirit is
                    gonna allow the hand, and the foot, and
MAKE INSTALL NOT WAR            the mouth, just to begin to speak, and
                                        to minister, and to heal coordinated by
                    the head.

I use UNIX because reboots are for hardware upgrades.

           -- Waiting for FreeBSD 3.1, not Godot --