[llvm] Correct .dynstr finding of getDynamicStrTab() (PR #127975)

[James Henderson via llvm-commits]

https://github.com/jh7370 approved this pull request.

LGTM too. Do you need assistance with merging it?

I'd be tempted to update the PR description to avoid people needing to click links to get the context. Something along the lines of "the dynamic string table used by the dynamic section is referenced by the sh_link field of that section, so we should use that directly, rather than going via the dynamic symbol table." Also, I'd add `[llvm-objdump]` to the PR title.

https://github.com/llvm/llvm-project/pull/127975