[DWARF5] Added support for emission of .debug_macro.dwo section

This patch adds support for emission of following DWARFv5 macro
forms in .debug_macro.dwo section:

- DW_MACRO_start_file
- DW_MACRO_end_file
- DW_MACRO_define_strx
- DW_MACRO_undef_strx

Reviewed By: dblaikie

Differential Revision: https://reviews.llvm.org/D78866