build: fix hpux build pb

build: fix hpux build pb

Pair-Programmed-With: Thomas Nagy <tnagy2pow10@gmail.com>

Fix the library extension from .so to .sl
Add full path to library when linking this is needed due to a strange
behavior of HP-UX:

This command: gcc demo demo.c -L dir1/dir2/ -lsomelib
will give a binary with a hard coded lib like dir1/dir2/libsomelib.sl.
Somehow like a partial rpath, it has the first impact of fooling waf
detection of wether the plateform support libraries or not (leading to
being unable to compile samba on HPUX) and the impact of having non
functionnal binaries.

Autobuild-User: Matthieu Patou <mat@samba.org>
Autobuild-Date: Wed Dec  8 00:32:50 CET 2010 on sn-devel-104