[lld] [lld][ELF] Add --debug-names to create merged .debug_names. (PR #86508)

[via llvm-commits]

cmtice wrote:

I've updated the tests and  created a the requested new tests, except for one where comp_unit count > 1 -- still working on that one.

New tests added:
 - ppc32-debug-names.s : tests big-endian and 32-bit.
 - debug-names-missing-parent.s : tests when an entry doesn't have a DW_IDX_parent attribute.
Updated the following test to include testing of --noinhibit-exec: debug-names-bad-name-count.s & debug-names-bad-die-idx-sizes.s

I've also updated all the tests to use shorter/better file & directory names.

I tried very hard to craft a test for the error for  'if (locs.EntriesBase > namesExtractor.getData().size())', but was unable to create one;  either my changes would cause NameIndex::extract() to error out. before we get to this code; or it would trigger the other ' index entry out of bounds' error , but not this one. I'm open to suggestions.

https://github.com/llvm/llvm-project/pull/86508