[llvm] [MachO] Refine alias n_desc flag ownership (name flags from alias, not aliasee) (PR #212001)

[Folkert de Vries via llvm-commits]

folkertdev wrote:

We don't actually have strong aliases on Mach-O though right? Still good to fix of course.

Empirically strong aliases do appear to work, so I might add add support to https://github.com/llvm/llvm-project/pull/211539 once this lands.

@cofibrant you mentioned 

> especially without a sign off from one or more Mach-O experts.

Did you have anyone in particular in mind? 

https://github.com/llvm/llvm-project/pull/212001