[llvm] Wasm: add support for `swifttailcc` calling convention (PR #188296)

[Derek Schuff via llvm-commits]

dschuff wrote:

@MaxDesiatov @kateinoigakukun I just noticed on another Wasm PR we got a sanitizer failure of the swiftcc test: https://github.com/llvm/llvm-project/pull/180263#issuecomment-4173777405
It doesn't look exactly related to this change, but do you mind taking a look?

https://github.com/llvm/llvm-project/pull/188296