#[cfg(...)] flags don't work

[thejpster]

The #[cfg(...)] flags don't work, which I think is because we don't set them in the build.rs file. I think we need to copy the relevant code from the cortex-m/build.rs file.

This affects armv8m-main because without #[cfg(armv8)] you don't get a SecureFault handler.

[thejpster]

See #182

[jonas-schievink]

It looks like the cfg flag is now set properly:

cortex-m-rt/build.rs

Lines 53 to 55 in 7c8778f

	} else if target.starts_with("thumbv8m") {
	println!("cargo:rustc-cfg=cortex_m");
	println!("cargo:rustc-cfg=armv8m");

[thejpster]

Yup. Looks like I fixed it already.