[ELF] Add elf64lppc emulation.

[ruiu]

I think this patch should be checked in with a trivial test case that generates a minimal binary file for ppc64le.

[MaskRay]

Add elf64lppc to emulation.s

[ruiu]

LGTM

But I think further efforts should be made with a coordination with other people who are working on PPC, so that no duplicate efforts are made.

[MaskRay]

In D44264#1033235, @ruiu wrote:

LGTM

But I think further efforts should be made with a coordination with other people who are working on PPC, so that no duplicate efforts are made.

Thx.
e.g. coordinate with PPC, ARM, HPPA, METAG people for the --stub-group-size= option..

ELF/Driver.cpp

std::pair<ELFKind, uint16_t> Ret =
           .Cases("armelf", "armelf_linux_eabi", {ELF32LEKind, EM_ARM})
           .Case("elf32_x86_64", {ELF32LEKind, EM_X86_64})
           .Cases("elf32btsmip", "elf32btsmipn32", {ELF32BEKind, EM_MIPS})
           .Cases("elf32ltsmip", "elf32ltsmipn32", {ELF32LEKind, EM_MIPS})
           .Case("elf32ppc", {ELF32BEKind, EM_PPC})
           .Case("elf64btsmip", {ELF64BEKind, EM_MIPS})
           .Case("elf64ltsmip", {ELF64LEKind, EM_MIPS})
           .Case("elf64ppc", {ELF64BEKind, EM_PPC64})
+          .Case("elf64lppc", {ELF64LEKind, EM_PPC64})
           .Cases("elf_amd64", "elf_x86_64", {ELF64LEKind, EM_X86_64})
           .Case("elf_i386", {ELF32LEKind, EM_386})
           .Case("elf_iamcu", {ELF32LEKind, EM_IAMCU})
           .Default({ELFNoneKind, EM_NONE});
 
   if (Ret.first == ELFNoneKind)
     error("unknown emulation: " + Emul);
   return std::make_tuple(Ret.first, Ret.second, OSABI);