[clang] [WebAssembly] Update generic CPU configuration to include nontrapping-fptoint (PR #67459)

[Sam Clegg via cfe-commits]

sbc100 wrote:

@kripken @dschuff @sunfishcode, can you remember why we didn't include this is part of https://reviews.llvm.org/D125728 and https://reviews.llvm.org/D125729?   Has the landscape changed enough since then that we can/should land this now?

https://github.com/llvm/llvm-project/pull/67459