[clang] [Clang][Parser] Reject unbalanced unknown attribute arguments (PR #220259)

[via cfe-commits]

nehaGautam07 wrote:

Dropped SkipBalancedAttributeArgs in favor of an opt-in SkipUntil flag
(StopAtUnbalanced), as requested. It is only used for unknown [[]] / C23
attribute argument skipping. Other SkipUntil call sites are unchanged.

@AaronBallman this is the flag approach you and Corentin suggested.

@erichkeane the implementation is now the smaller flag.

https://github.com/llvm/llvm-project/pull/220259