Use rust-toolchain while outside of project directory?

[Klaaktu]

Sorry for the off-topic, but...

When I try:
RUSTFLAGS="-C target-cpu=native" cargo build --release --bin ssserver --manifest-path ~/shadowsocks-rust-master/Cargo.toml
It says:
error[E0554]: `#![feature]` may not be used on the stable release channel

cd into the directory works fine. Is there a way to let cargo use rust-toolchain while outside of project directory?

[kallydev]

Just use one line command to download specified version and set it as default.

rustup default nightly-2021-09-10