Right now, we are able to spawn a gdbserver from inside code so we can debug with gdb using jstests or in other situations where running `gdb ./mongod` is not convenient/possible. This handy feature does not work on MacOS, since their gdb package does not contain gdbserver.

I propose adding the ability to do the same thing with LLDB's debugserver, which functions mostly the same way. This way, we can use this debugging functionality on MacOS.

I have gotten it to work on my Macbook, but theoretically this should be able to work fine on any other operating system that supports LLDB as well.

I have a PoC here, which would obviously need changes (like not having a hardcoded path) before it were committed to master

https://gist.github.com/super-cooper/6c3be5e6e06949ab4af32c31babe9f17