contrib/gdb-add-index.sh -dwarf-5

contrib/gdb-add-index.sh -dwarf-5

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(gdb) help save gdb-index
Save a gdb-index file.
Usage: save gdb-index [-dwarf-5] DIRECTORY

No options create one file with .gdb-index extension for pre-DWARF-5
compatible .gdb_index section.  With -dwarf-5 creates two files with
extension .debug_names and .debug_str for DWARF-5 .debug_names section.
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But gdb-add-index command provided no way how to pass the -dwarf-5 option.

gdb/ChangeLog
2018-07-07  Jan Kratochvil  <jan.kratochvil@redhat.com>

	* contrib/gdb-add-index.sh ($dwarf5): New, use it.