[clang] [-Wunsafe-buffer-usage] Fix assert when constexpr size passed to snprintf() (#119786) (PR #124022)

[Ziqing Luo via cfe-commits]

https://github.com/ziqingluo-90 approved this pull request.

Thank you for the fix! I am curious if you have a counterexample?  Because I thought that `Size` must have an integral type.

https://github.com/llvm/llvm-project/pull/124022