rust flags are vastly different between linux flake devshell and cargo config.toml ?

[jedesroches]

While investigating #13040, I found that there are (at least ?) two places from which flags for rustc are set in the project.

flake.nix devshell

• -C link-arg=-fuse-ld=lld
• -C target-cpu=native
• -C link-arg=-Wl,--no-rosegment
• --cfg tokio_unstable

config.toml

• --cfg tokio_unstable
• -C target-feature=-crt-static

Comparison

Only the tokio_unstable config flag seems to appear on both sides. Without being a very experienced rustacean at all, it still strikes me as rather strange the flags would be so different between linux and all other targets... Is this expected ?

[jedesroches]

As an additional remark, the flags are set via export calls in the shellHook, rather than just set in the env attribute. Is there a reason for this ?