[llvm] [TableGen] Rework error reporting for duplicate Feature/Processor. (PR #102257)

[Rahul Joshi via llvm-commits]

jurahul wrote:

> This seems like a (minor) regression in functionality, essentially reporting two random instances out of order. It would be nice if the order was preserved. Could you use line number as the tie breaker in the sort?

Also note that this is not true. The records vended out by getAllDerivedDefinitions() are sorted by name and not their lexical order, so even in the previous case the "Previous" definition could have been a later on.

https://github.com/llvm/llvm-project/pull/102257