fix: only use jemalloc on linux

[tobz]

Summary

When running ADP on macOS, it would immediately crash due to an error coming from jemalloc:

<jemalloc>: No THP support: thp:never
<jemalloc>: Abort (abort_conf:true) on invalid conf value (see above).

We previously disabled THP support in jemalloc to deal with ballooning RSS but, seemingly, jemalloc considers it a completely invalid configuration when on macOS instead of just ignoring, thus the abort.

This PR simply moves our usage of jemalloc to be gated behind #[cfg(target_os = "linux")]. In the future, it'd be nice to just adjust our compile-time jemalloc configuration string for macOS to not include the thp:never bit, but the Cargo configuration file schema doesn't support per-target environment variables, so we don't have an easy way to do so... yet, at least.

Change Type

• Bug fix
• New feature
• Non-functional (chore, refactoring, docs)
• Performance

How did you test this PR?

Built ADP locally on both macOS and Linux and ensured they ran correctly without throwing an error at startup.

References

N/A