Back when specific control of the Rust version used with RIOT was needed, CARGO_CHANNEL was added to explicitly set the Rust version with consideration for CI special cases. Rust's mechansims of selecting a toolchain can be used instead now.
native
Updating the Makefiles for example and test applications to set the TERMFLAGS correctly for native.
Closes: https://github.com/RIOT-OS/RIOT/issues/18500
Taken and simplified from shell test.