X86: handle external tail calls in Windows JIT

If there was a tail call, we would incorrectly handle the relocation.  It would
end up indexing into the array with an incorrect section id.  The symbol was
external to the module, so the Section ID was UNDEFINED (-1).  We would then
index the SmallVector with this ID, triggering an assertion.  Use the Value
rather than the section load address in this case.

llvm-svn: 275442