[clang-tools-extra] [clang-tidy] Option to ignore anonymous namespaces in avoid-non-const-global-variables (PR #93827)

[Pascal Jungblut via cfe-commits]

pascalj wrote:

Thanks for your feedback!

>     * what about "static" non const global variables

Good point, forgot about these. If both are allowed, it is more about the internal linkage than it is about the namespace. I renamed the option to `AllowInternalLinkage` and permit variables in anonymous namespaces and static global variables, since they're equivalent (AFAICT). 

> I'm fine for having an options that control behavior of the check. But please note that there are other aspects of "I.2: Avoid non-const global variables" rule that anonymous namespace or static does not solve. Like race-conditions in multithread env. Or even to force developer not to use global objects to pass data between functions.
> 
> Even that I see many times that warnings from this check are being nolinted, I still think that it's doing good job.

I completely agree with both you and @carlosgalvezp: this is neither an option that should be enabled by default, nor should people prefer it over nolinting without some thought. However, I see not much harm in giving someone the choice to do so. In the end, all of clang-tidy's checks are optional to some degree.

Having said that: if the maintainers prefer not to have this option, this is also fine with me.

https://github.com/llvm/llvm-project/pull/93827