[llvm-jitlink] Link libnetwork on Haiku in llvm-jitlink

The system's network API is in libnetwork.so, so we explicitly need to link to
them on Haiku. This patch is similar to https://reviews.llvm.org/D97633.

Patch by Niels Reedijk. Thanks Niels!

Reviewed By: lhames

Differential Revision: https://reviews.llvm.org/D98405