[clang] [llvm] [MC] Emit a jump table size section (PR #101962)

[Fangrui Song via llvm-commits]

MaskRay wrote:

Conventionally, `.debug_*` sections are reserved for DWARF, even without official standards.
GNU strip's default behavior --strip-all, emulated by llvm-objcopy's --strip-all-gnu option, is roughly to remove non-SHF_ALLOC sections that are not debug.
The `.llvm` prefix holds no special meaning.

When designing new sections, we should not adapt to the --strip-all-gnu behavior.

Jump tables exhibit diverse structures. For instance, consider llvm/test/CodeGen/ARM/jump-table-tbh.ll and Mach-O's .data_region.


https://github.com/llvm/llvm-project/pull/101962