[clang] [compiler-rt] Reland "[Clang][CodeGen] Report when an alias points to an incompatible target" (PR #195550)

[Eli Friedman via cfe-commits]

efriedma-quic wrote:

> So this applies to types, but differently named structs with identical contents aren't considered equal

Yes, this is computing equivalence using C "compatible type" rules (which say that the name of the struct is significant, but the name of a typedef is not).  The big advantage of this form of equivalence is that we can use the existing implementation. :)

https://github.com/llvm/llvm-project/pull/195550