[clang] Fixed two typos: "__builin_" --> "__builtin_" (PR #98782)

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

LGTM.

Hmm, it seems like this somehow flew under the radar (I also just randomly happened to see this while looking for something else just now). 

In the future, feel free to add a comment with ‘ping’ or something along those lines to the pr every week or so (or message us on the LLVM Discord etc. if you get absolutely no response after a while); we have so many prs that some just go unnoticed unfortunately... :(

https://github.com/llvm/llvm-project/pull/98782