[llvm] [WebAssembly] Limit increase of Ctx.End (PR #76676)

[via llvm-commits]

DavidKorczynski wrote:

To a large extent I'm coming from the angle of an issue was reported by [OSS-Fuzz](https://github.com/google/oss-fuzz) so I added a fix.

I assume once this bug is fixed the fuzzer will quickly report others. I'm not sure about the threat model, but for what it's worth the majority of issues I previously fixed from this fuzzer occurred in [WasmObjectFile.cpp](https://github.com/llvm/llvm-project/blob/main/llvm/lib/Object/WasmObjectFile.cpp) as opposed to the other files in `llvm/lib/Object/`. However, for some perspective, the fuzzer that found it was added to LLVMs codebase roughly 9 years ago https://github.com/llvm/llvm-project/blob/main/llvm/tools/llvm-dwarfdump/fuzzer/llvm-dwarfdump-fuzzer.cpp The issues reported by this fuzzer are here: https://bugs.chromium.org/p/oss-fuzz/issues/list?q=llvm-dwarfdump-fuzzer&can=1&sort=-reported and are public (the OSS-Fuzz integration was configured to be public).

https://github.com/llvm/llvm-project/pull/76676