[clang] [Sparc] Add flags to enable errata workaround pass for GR712RC and UT700 (PR #104742)

[Fangrui Song via cfe-commits]

MaskRay wrote:

This patch looks ok, but I expect justification why we need these -mfix-* options, which adds some, even if little, burden to the generic code.
I asked because these are apparent workarounds. Sparc is a very old port that doesn't receive lots of development, and we should carefully balance needs and maintenance burden.

https://github.com/llvm/llvm-project/pull/104742