[llvm] [WebAssembly] Disallow tail calls with byval arguments (PR #125142)

[Thomas Lively via llvm-commits]

tlively wrote:

Probably, but I don't understand those issues :) Can you help explain what bad situation the double copy avoids?

I've also added some tests for edge cases we would have to handle if we tried to do the argument forwarding optimization. That optimization seems more complex than I had initially hoped, so I'd rather not tackle it in this PR.

https://github.com/llvm/llvm-project/pull/125142