[llvm] [dsymutil] Add option to copy swiftmodules built from interface (PR #165293)

[Roy Shi via llvm-commits]

royitaqi wrote:

@adrian-prantl:

Discussed with @rmaz. We land on the following plan:
* For now, we will still merge this patch and cherry-pick internally to get the issue fixed. It's affecting our users on a daily basis.
* For longer term, we will be happy to adopt your solution once it's shipped. It's a simpler (and thus better) solution.

https://github.com/llvm/llvm-project/pull/165293