resolve relative paths for configuration paths

[dotcarmen]

in my os project, i use a submodule for the zig repo to

1. avoid hard-coding paths to local git directories
2. include all commits from ongoing PRs (i have a DEV branch which merges all such PRs)
3. avoid loading build.zig from the zig repo, since it's unnecessary and causes my project's build.zig to fail to build (since i use zig 0.14 to build my project, only diverging with std)

it'd be nice to support this automatically with editor configurations. for example, in the latest commit of my os project, i included a zls.json that sets the zig lib dir to the one in the submodule.

[dotcarmen]

note that the os project is my only project currently that uses anything besides standard zig 0.14. it's gotten pretty annoying having to mv ~/Library/Application\ Support/zls.json{,.bak} and back (and subsequent restarting of the LSP) every time i want to work on my os project, so i'm just trying to squash some config issues :)