dwarf_add_AT_const_value_string(3) on FreeBSD
The text 61cb01a5309a, as FreeBSD 12.0-RELEASE, FreeBSD 11.4-RELEASE, FreeBSD 11.3-RELEASE, FreeBSD 11.2-RELEASE, FreeBSD 11.1-RELEASE, FreeBSD 11.0-RELEASE shipped it.
create and attach a DW_AT_const_value attribute