[llvm-readobj] MachO -- dump LinkerOptions load command.

Example output:

Linker Options {
  Size: 32
  Count: 2
  Strings [
    Value: -framework
    Value: Cocoa
  ]
}

There were only two tests using this -- so I converted them as part of
this commit rather than separately.

Differential Revision:	 http://reviews.llvm.org/D12702

llvm-svn: 247106