We briefly referred to being able to specify --target=binary without
explaining what binary input/output meant. This change adds a section on
this.
Reviewed by: MaskRay, abrachet
Differential Revision: https://reviews.llvm.org/D64245
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@365312 91177308-0d34-0410-b5e6-96231b3b80d8