[llvm] WebAssembly: Take the exception model from the module flag (PR #227583)

[Derek Schuff via llvm-commits]

dschuff wrote:

> > Had to hack in the TargetOptions field to preserve the clang test behavior, which will be removed in the next change
> 
> which should be reverted here before submitting, it wasn't actually enough to fix the clang test. that requires #228372

in other words, you mean that #228732 is freestanding and can land first?

https://github.com/llvm/llvm-project/pull/227583