Separate debug info from .so file

[Mothblocks]

After #119, the release build of librust_g.so is 70 MB as opposed to the previous 10 MB.

This is extremely unideal. There are two ways I see to solve this.

One is that we make release w/ debug info a separate target, then ship both librust_g.so and librust_g_debug_info.so.

Another is that there might be a way to split it into its own file much like the .pdb. There's a few StackOverflow posts about this, something about objcopy? Not sure how doable it is but that would be ideal if it's feasible