Update the parameters passed to the assembler and linker for
the PPC64LE target.  Specifically:
(assembler) adds/uses  -mppc64 -mlittle-endian
(linker) adds/uses  elf64lppc

Testcase included.



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@204626 91177308-0d34-0410-b5e6-96231b3b80d8