[Bug target/83743] -mcpu=native causes gcc to exit in error if cpu is not recognized

[segher at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83743

--- Comment #4 from Segher Boessenkool <segher at gcc dot gnu.org> ---
Which is perfectly fine, except the error message is a bit confusing if you
don't know what's going on.