[clang] [llvm] [Driver] Default -msmall-data-limit= to 0 and clean up code (PR #83093)

[Fangrui Song via cfe-commits]

MaskRay wrote:

Thanks! I'll land this in a few days.

I believe it's now up to the gp default users to justify the default and why they cannot user a Clang configuration file (this is difficult to justify, as we've many many decisions to Clang configuration files). I think this is important to ensure that future sdata/sbss development like #87040 not cause disruption to users who don't use the feature.

https://github.com/llvm/llvm-project/pull/83093