Rework to let RuntimeDyld/X86/MachO_x86-64_PIC_relocations.s pass on win32.

FIXME: "llvm-rtdyld -verify -check" is still sensitive to path separator.
Fix searching StubMap to be tolerant of both '/' and '\\' on Win32.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@213723 91177308-0d34-0410-b5e6-96231b3b80d8