Snapbox's polyfill for `CARGO_RUSTC_CURRENT_DIR` looks for the furthest
away `Cargo.toml`.
That works in our repo but won't work as a submodule in rustc.
This uses the `config.toml` hack for setting the variable.
I verified
- Without this, the polyfill is used
- With this, it is used
- Without this on nightly, the official `CARGO_RUSTC_CURRENT_DIR` is
used
This will allow running an xtask without requiring building the world.
In most cases, a user will already have been building cargo but not in
CI.
The packages keep an `xtask-` prefix to help raise awareness of them but
exposed as `cargo <suffix>` to avoid having a direction proxy to wrap
`cargo run -p xtask-<suffix>` as `cargo xtask <suffix>`.
Ed Page
Weihang Lo