reuqest support for rust-toolchain-nightly.toml #4659

Problem you are trying to solve

Our project normally uses the stable channel. However, some cross-compiled targets need to use the nightly channel. However, there currently seems to be no way to fix both channels at the same time.

Can you consider adding a rust-toolchain-nightly.toml file to use the fixed version of the nightly channel when using cargo +nightly

Solution you'd like

$ cargo --version 
1.85.0
$ cargo +nightly --version
nightly-1.85.0-2025-03-05 # defined in the rust-toolchain-nightly.toml file

Notes

No response