Hi all,

This patch adds or fixes support for various AMD 'isa' and 'arch' trait 
selectors, so as to be consistent with LLVM. It also adds test cases 
checking all supported AMD ISAs are properly recognised when used in a 
'metadirective' construct.

This patch is closely related to 
https://gcc.gnu.org/r13-4403-g1fd508744eccda but cannot be committed to 
mainline because metadirectives and dynamic context selectors have not 
landed there yet.

Can this be committed to OG12?

Thanks,