Add a default directory to RUST_TARGET_PATH

[emberian]

It's possible that we want some sort of system-wide installation of target specifications.

[steveklabnik]

Would this change need an RFC? I'm inclined to say so, but I'm not sure.

[emberian]

No, this is purely a rustc thing. Target specs can't ever be part of the language spec.

[steveklabnik]

Triage: not aware of a change here.

[kevinmehall]

What if it tried <sysroot>/lib/rustlib/<target name>/target.json instead of or in addition to a fixed directory? That way you could install a target specification and the associated libraries by unpacking a single directory.

[emberian]

This was clarified in a recent PR, let me find it.

[emberian]

#31117

[xobs]

This issue is mentioned in src/librustc_target/spec/mod.rs:1271 as being a FIXME. There still doesn't appear to be any sort of sane default search path.

I like @kevinmehall 's approach, which tucks the target.json inside the sysroot, making it easy to distribute. I'd also vote for adding . to the list.

Should this issue be reopened, since it was closed without any solution?