elfclassify: Add --any-ar-member option to classify archive member

elfclassify: Add --any-ar-member option to classify archive member

To determine whether an ELF archive contains a member of a particular
type add a new input option to eu-elfclassify --any-ar-member.
eu-elfclassify will match if a given file is an ELF archive and the
classification options apply to at least one of the members.

This can be used for example to check whether an ELF archive file
contains ELF members that can be stripped by using:

  eu-elfclassify --ar-member --unstripped <ar-file>

	* src/elfclassify.c (current_path): Drop const.
	(flag_ar_member): New static bool.
	(classify_flag_ar_member): new enum member.
	(parse_opt): Handle classify_flag_ar_member.
	(check_checks): New function taken from...
	(process_current_path): ...here.
	(check_ar_members): New function.
	(main): Add ar-member to options. Update argp.doc.
	* tests/run-elfclassify.sh: Add various --any-ar-member tests.

Signed-off-by: Mark Wielaard <mark@klomp.org>