Not sourcing `target-cpu`

[N-T-K]

If TARGET = Some(thumbv7em-none-eabihf) then it is correctly mapped to:

cc-rs/src/lib.rs

Lines 2406 to 2412 in 1ca8b2a

	if target.full_arch.starts_with("thumbv7em") {
	cmd.args.push("-march=armv7e-m".into());
	if target.abi == "eabihf" {
	cmd.args.push("-mfpu=fpv4-sp-d16".into())
	}
	}

However, if there is a provided CARGO_ENCODED_RUSTFLAGS = Some(-Ctarget-cpu=cortex-m7) then the aforementioned cc flags are wrong and should be -march=armv7e-m+fp.dp -mfloat-abi=hard -mfpu=auto.

gcc -mcpu docs.
rustc thumbv7em-none-eabihf.

[NobodyXu]

I would accept a PR to fix this

[N-T-K]

It's a bit more complicated now that I've looked into it, but I'll try and put something together.