[llvm] IR: Introduce "exception-model" module flag (PR #220052)

[Douglas Yung via llvm-commits]

dyung wrote:

Hi @arsenm, this change seems to be causing a test failure in the test `Transforms/Util/DeclareRuntimeLibcalls/basic.ll` on MacOS. Can you take a look?

https://lab.llvm.org/buildbot/#/builders/190/builds/50035

https://github.com/llvm/llvm-project/pull/220052