Stop objcopy from corrupting mach-o files.

	PR 23299
	* mach-o.c (cputype): New function.
	(cpusubtype): New function.
	(bfd_mach_o_bfd_print_private_data): New function.  Dispalys the
	values in the MACH-O file header.
	(bfd_mach_o_bfd_copy_private_header_data): Copy the cputype and
	cpusubtype fields from the input bfd's mach-o header to the output
	bfd.
	* mach-o-target.c (bfd_mach_o_bfd_print_private_bfd_data):
	Redefine to bfd_mach_o_bfd_print_private_data.
	* mach-o.h (bfd_mach_o_bfd_print_private_bfd_data): Prototype.