Build fails on distros with elfutils < 0.170

[jallen-amd]

On distros with elfutils version < 0.170 (SLES 15 SP3 for example), dwarves fails to build with the following error:

dwarf_loader.c:2529:13: error: ‘DW_TAG_skeleton_unit’ undeclared (first use in this function); did you mean ‘DW_TAG_type_unit’?
  if (tag == DW_TAG_skeleton_unit) {
             ^~~~~~~~~~~~~~~~~~~~
             DW_TAG_type_unit

433dc78 Adds the definition for DW_TAG_skeleton_unit only if the elfutils version is >= 0.170, but 0135ccd uses the tag regardless of the elfutils version.