problem installing packs with foreign code

Hi all,
I wonder if people have had any success installing packages which
include C code that needs to be built?
I've tried prosqlite and the environ test package, and in both cases,
the linker fails with "library not found for -lswipl".
This seems to be because the build environment does not
include any library path flag - I would expect, eg for my system,

	-L/usr/local/lib/swipl-6.5.1/lib/x86_64-darwin11.4.2

In my own test pack Makefile, I build with swipl-ld so it works fine, but in
the case that there are multiple SWI installations, I have no guarantee that 
I'm calling the swipl-ld that belongs to the swipl that is currently running.

Samer.