Update LLVM prebuilts for rebase to r212749.

Change-Id: I4ab2a7671522d6d8c52e9ade72591f189f5a1670
diff --git a/renderscript/clang-include/stdarg.h b/renderscript/clang-include/stdarg.h
index 6110a06..a57e183 100644
--- a/renderscript/clang-include/stdarg.h
+++ b/renderscript/clang-include/stdarg.h
@@ -44,7 +44,9 @@
 #endif
 
 /* Hack required to make standard headers work, at least on Ubuntu */
+#ifndef __GNUC_VA_LIST
 #define __GNUC_VA_LIST 1
+#endif
 typedef __builtin_va_list __gnuc_va_list;
 
 #endif /* __STDARG_H */