macos: use GAUDI_LIBRARY_PATH instead of LD_...
This is a quick, macOS-only implementation of the suggestion in #251 , finally fixing Gaudi on macOS for me (after setting export GAUDI_LIBRARY_PATH=$LD_LIBRARY_PATH
)
Should be safe to merge as the changes are only inside APPLE ifdefs, but does make the code a bit more complicated.
Edited by Valentin Volkl