This broke building the TSan runtime on Mac, see comment on
5548843d69
> so that they get an error on other targets. This change uses let statements to
> apply `Flags = [TargetSpecific]` to options (mostly -m*) without specifying `Flags`.
> Follow-up to D151590.
>
> For some options, e.g. -mdefault-build-attributes (D31813), -mbranch-likely
> (D38168), -mfpu=/-mabi= (6890b9b71e525020ab58d436336664beede71575), a warning
> seems desired in at least certain cases. This is not the best practice, but this
> change works around them by not applying `Flags = [TargetSpecific]`.
>
> (
> For Intel CPU errata -malign-branch= family options, we also drop the unneeded
> NotXarchOption flag. This flag reports an error if the option is used with
> -Xarch_*. This error reporting does not seem very useful.
> )
This reverts commit 5548843d692a92a7840f14002debc3cebcb3cdc3.
b18ca7296e