1. [DWARFYAML] Make the debug_str section optional. (details)
Commit 428b2ffad4a346a967a4a105356fbc0fa518e2cc by Xing
[DWARFYAML] Make the debug_str section optional.

This patch makes the debug_str section optional. When the debug_str
section exists but doesn't contain anything, yaml2obj will emit a
section header for it.

Reviewed By: grimar

Differential Revision:
The file was modifiedllvm/test/tools/yaml2obj/ELF/DWARF/debug-str.yaml (diff)
The file was modifiedllvm/include/llvm/ObjectYAML/DWARFYAML.h (diff)
The file was modifiedllvm/lib/ObjectYAML/DWARFYAML.cpp (diff)
The file was modifiedllvm/tools/obj2yaml/dwarf2yaml.cpp (diff)
The file was modifiedllvm/lib/ObjectYAML/DWARFEmitter.cpp (diff)
The file was modifiedllvm/test/ObjectYAML/MachO/DWARF-debug_str.yaml (diff)