[llvm] [dyndbg] Create .debug_llvm_dyndbg section without any section flags (PR #194855)

[Orlando Cazalet-Hyams via llvm-commits]

OCHyams wrote:

This adds a contract between Clang and LLVM that the nested-ELF section name will be called ` .debug_llvm_dyndbg`. If the metadata approach is preferable to eliminate that, I'm happy to go that route.

https://github.com/llvm/llvm-project/pull/194855