[llvm] [llvm-strings] Add --encoding & --unicode options (PR #221794)

[James Henderson via llvm-commits]

jh7370 wrote:

Oh, also, I haven't looked at how intertwined the implementation is, but it might be worth considering how to split this up into multiple smaller PRs in a stack of some variety. Each would implement one or more of the sub-option values, so that we don't have to review them all in one go.

https://github.com/llvm/llvm-project/pull/221794