Allow setting install backend in bunfig

[b0o]

What is the problem this feature would solve?

I want to be able to globally set the install backend to symlink due to the particular way the filesystem on my machine is set up. Basically, I want this:

~/my-proj/node_modules/path/to/dep/file.js -> ~/.cache/.bun/install/cache/path/to/dep@version/file.js

Currently, bun is using hardlinks instead of symlinks, which is problematic in my setup.

What is the feature you are proposing to solve the problem?

I'd like the ability to set the install backend in ~/.config/.bunfig.toml:

[install]
backend = "symlink"

What alternatives have you considered?

Running bun install --backend=symlink does what I want. I just want to be able to set this option in my global bunfig.