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: NKees Cook <keescook@chromium.org>
Co-developed-by: NAlex Gaynor <alex.gaynor@gmail.com>
Signed-off-by: NAlex Gaynor <alex.gaynor@gmail.com>
Co-developed-by: NWedson Almeida Filho <wedsonaf@google.com>
Signed-off-by: NWedson Almeida Filho <wedsonaf@google.com>
Co-developed-by: NDavid Gow <davidgow@google.com>
Signed-off-by: NDavid Gow <davidgow@google.com>
Signed-off-by: NMiguel Ojeda <ojeda@kernel.org>