[llvm] [WebAssembly] Enable multivalue return when multivalue ABI is used (PR #88492)

[Cheng Shao via llvm-commits]

TerrorJack wrote:

There are other reasons why those flags couldn't be easily added, though that'll distract the discussion here. Anyway thanks for the suggestion @aheejin and this patch doesn't break stuff for us, so feel free to land at your convenience :)

https://github.com/llvm/llvm-project/pull/88492