[clang] [NFC][clang] Split clang/lib/CodeGen/CGBuiltin.cpp into target-specific files (PR #132252)

[Sergei Barannikov via cfe-commits]

https://github.com/s-barannikov commented:

Apparently my English is really not that good, sorry :smile: 
Please see the two inline suggestions


https://github.com/llvm/llvm-project/pull/132252