[clang] Include [[clang::require_explicit_initialization]] warnings in system headers (PR #141133)

[Aaron Ballman via cfe-commits]

AaronBallman wrote:

> Hi all! So given the discussion above and that @erichkeane also okayed this, can we finally proceed with this PR? I'd like to note that after discussing it for the past month and a half, it still seems like we have no idea what the ideal solution to the more-general problem could even look like in principle (if it's even possible), never mind how to get there in practice. Whereas this particular solution would address the issue we're facing, without closing the door to any improvements we may think of later.

Yeah, I think we should move forward. This may not be ideal, but we also don't know what ideal will be and this is solving a problem.

Thank you for the really good discussion on this! I know it's frustrating to have long-running discussions, but we try to have a high bar for quality and that sometimes leads to this kind of thing, so we appreciate all the consideration given here,

https://github.com/llvm/llvm-project/pull/141133