This patches LLVM to use ELFv2 on ppc64 uncoditionally unless overridden. We
need this because unlike most distros we use ELFv2 for both glibc and musl
on big endian ppc64.

--- a/lib/Target/PowerPC/PPCTargetMachine.cpp
+++ b/lib/Target/PowerPC/PPCTargetMachine.cpp
@@ -197,9 +197,9 @@ static PPCTargetMachine::PPCABI computeTargetABI(const Triple &TT,
 
   switch (TT.getArch()) {
   case Triple::ppc64le:
-    return PPCTargetMachine::PPC_ABI_ELFv2;
   case Triple::ppc64:
-    return PPCTargetMachine::PPC_ABI_ELFv1;
+    /* we use elfv2 by default for both endians and both libcs */
+    return PPCTargetMachine::PPC_ABI_ELFv2;
   default:
     return PPCTargetMachine::PPC_ABI_UNKNOWN;
   }