[ELF/AArch64] Accept -m aarch64linux.

This option is passed by clang driver if the target triple
is "aarch64-unknown-linux".

Differential Revision: http://reviews.llvm.org/D14831

llvm-svn: 253639
diff --git a/lld/ELF/Driver.cpp b/lld/ELF/Driver.cpp
index 6bc7403..f1aaa5b 100644
--- a/lld/ELF/Driver.cpp
+++ b/lld/ELF/Driver.cpp
@@ -50,6 +50,8 @@
     return {ELF32LEKind, EM_386};
   if (S == "elf_x86_64")
     return {ELF64LEKind, EM_X86_64};
+  if (S == "aarch64linux")
+    return {ELF64LEKind, EM_AARCH64};
   error("Unknown emulation: " + S);
 }