Fix redundant comparison in gcc::Common::ConstructJob.

We were checking "Arch == llvm::Triple::x86_64 || Arch
== llvm::Triple::x86_64", but the rhs should actually check for
powerpc64.

Found while experimenting with a potential new Clang warning.

llvm-svn: 177496
diff --git a/clang/lib/Driver/Tools.cpp b/clang/lib/Driver/Tools.cpp
index 9a6a1f2..2a07c90 100644
--- a/clang/lib/Driver/Tools.cpp
+++ b/clang/lib/Driver/Tools.cpp
@@ -3631,7 +3631,7 @@
   // here.
   if (Arch == llvm::Triple::x86 || Arch == llvm::Triple::ppc)
     CmdArgs.push_back("-m32");
-  else if (Arch == llvm::Triple::x86_64 || Arch == llvm::Triple::x86_64)
+  else if (Arch == llvm::Triple::x86_64 || Arch == llvm::Triple::ppc64)
     CmdArgs.push_back("-m64");
 
   if (Output.isFilename()) {