libbacktrace: add Mach-O support

libbacktrace: add Mach-O support

libbacktrace/
	PR libbacktrace/88745
	* macho.c: New file.
	* filetype.awk: Recognize Mach-O files.
	* Makefile.am (FORMAT_FILES): Add macho.c.
	(check_DATA): New variable.  Set to .dSYM if HAVE_DSYMUTIL.
	(%.dSYM): New pattern target.
	(test_macho_SOURCES, test_macho_CFLAGS): New targets.
	(test_macho_LDADD): New target.
	(BUILDTESTS): Add test_macho.
	(macho.lo): Add dependencies.
	* configure.ac: Recognize macho file type.  Check for
	mach-o/dyld.h.  Don't try to run objcopy if we don't find it.
	Look for dsymutil and define a HAVE_DSYMUTIL conditional.
	* Makefile.in: Regenerate.
	* configure: Regenerate.
	* config.h.in: Regenerate.