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

[Alon Zakai via cfe-commits]

================
@@ -453,6 +453,8 @@ AIX Support
 
 WebAssembly Support
 ^^^^^^^^^^^^^^^^^^^
+The -mcpu=generic configuration now enables -nontrapping-fptoint. This
+proposals are standardized and available in all major engines.
----------------
kripken wrote:

```suggestion
proposal is standardized and available in all major engines.
```

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