Right now if a user wants to use extra LD_PRELOAD libraries (such as the soon-to-be-merged shadow_openssl_rng, they must add it to LD_PRELOAD in each simulated process's environment in the simulation config. Because LD_PRELOAD doesn't support shell expansion, the normal installation path of /home/<username>/.local/lib/... must be spelled out completely in the experiment config, including the literal username.

Maybe we should provide a more specialized config field for such preloads, and then handle it similarly to the shim: search for it in some expected places and then supply the full path where we found it to LD_PRELOAD.