Fix build.

The compilers had drifted a bit while I was away.

Change-Id: I938a5992e8e100f512db4c7934ac4b3ec80e8138
diff --git a/src/compiler/codegen/x86/X86RallocUtil.cc b/src/compiler/codegen/x86/X86RallocUtil.cc
index cd630a8..cdd75a1 100644
--- a/src/compiler/codegen/x86/X86RallocUtil.cc
+++ b/src/compiler/codegen/x86/X86RallocUtil.cc
@@ -185,4 +185,11 @@
     ((LIR*)lir)->flags.isNop = true;
 }
 
+extern RegLocation oatGetReturnAlt(CompilationUnit* cUnit)
+{
+    UNIMPLEMENTED(FATAL);
+    RegLocation res = LOC_C_RETURN;
+    return res;
+}
+
 }  // namespace art