[llvm] [BitcodeReader] Avoid integer overflow in strtab bounds check (PR #228786)

[Prasad Deshpande via llvm-commits]

Prasad-desh wrote:

Confirming I've read the contribution policies, including the LLVM AI Tool Use Policy. AI assistance (Claude) was used in preparing this patch and is noted at the end of the PR description. I reviewed the change myself and verified the behaviour of the old and new conditions before opening the PR.

https://github.com/llvm/llvm-project/pull/228786