PPC: Reinstate the fatal error when trying to emit a macho file.

llvm-svn: 168543
diff --git a/llvm/lib/Target/PowerPC/MCTargetDesc/PPCAsmBackend.cpp b/llvm/lib/Target/PowerPC/MCTargetDesc/PPCAsmBackend.cpp
index 1a58961..187c6b3 100644
--- a/llvm/lib/Target/PowerPC/MCTargetDesc/PPCAsmBackend.cpp
+++ b/llvm/lib/Target/PowerPC/MCTargetDesc/PPCAsmBackend.cpp
@@ -61,7 +61,9 @@
   void RecordRelocation(MachObjectWriter *Writer,
                         const MCAssembler &Asm, const MCAsmLayout &Layout,
                         const MCFragment *Fragment, const MCFixup &Fixup,
-                        MCValue Target, uint64_t &FixedValue) {}
+                        MCValue Target, uint64_t &FixedValue) {
+    llvm_unreachable("Relocation emission for MachO/PPC unimplemented!");
+  }
 };
 
 class PPCAsmBackend : public MCAsmBackend {