[clang] [LifetimeSafety] Don't enable lifetime suggestions via -Weverything (PR #232300)

[Balázs Benics via cfe-commits]

steakhal wrote:

I know that this is a fairly controversial patch - and it's fine if you don't agree with the motivation.
I only want to spark a discussion if your users have seen friction of this -Weverything and -Werror problems when living on mainline clang - or constantly backporting patches that your users rely on.

The alternative would be for us to keep a patch like this downstream - but I figured we all might share some common pain points. I also wanted to avoid going overly generic because that would certainly need an RFC and I don't really have the time for that right now.

So let me know what you think and how to have the cake and eat it too.
(Be discoverable via -Weverything, but also not break users who use -Weverything)

https://github.com/llvm/llvm-project/pull/232300