[llvm] [opt] Do not exit on first emitError (PR #194858)

[Matt Arsenault via llvm-commits]

arsenm wrote:

> Why exactly do we want to change this? If this diverges from llc, why do we not want to change llc to also bail on the first error, or just keep the divergence, especially if there are passes relying on this behavior?

Not immediately erroring is the correct way to handle errors, universally, for all tools. That is the production environment in clang (and any other sensible frontend). Immediately erroring degrades the usefulness of testing the error behaviors. It prevents catching crashes that occur after entering the invalid state, and necessitates annoying test file splitting to cover multiple error conditions 

https://github.com/llvm/llvm-project/pull/194858