scripts: add `generate_rust_target.rs`

This script takes care of generating the custom target specification
file for `rustc`, based on the kernel configuration.

It also serves as an example of a Rust host program.

A dummy architecture is kept in this patch so that a later patch
adds x86 support on top with as few changes as possible.

Reviewed-by: Kees Cook <[email protected]>
Co-developed-by: Alex Gaynor <[email protected]>
Signed-off-by: Alex Gaynor <[email protected]>
Co-developed-by: Wedson Almeida Filho <[email protected]>
Signed-off-by: Wedson Almeida Filho <[email protected]>
Co-developed-by: David Gow <[email protected]>
Signed-off-by: David Gow <[email protected]>
Signed-off-by: Miguel Ojeda <[email protected]>
2 files changed