Add to llvm-objdump the -no-leading-headers option with the use of the -macho option.

In some cases the leading headers of the file name, archive member and
architecture slice name in the output of lvm-objdump is not wanted so the
tool’s output can be directly used by scripts.  This matches the -X option
of the Apple otool(1) program.

rdar://28491674

llvm-svn: 288199