Fix another Mac build error.

Currently, Mac build failed with this message:
"art/src/compiler/codegen/arm/ArchUtility.cc:459: warning: format '%d'
expects type 'int', but argument 5 has type 'size_t'"

Change-Id: I9bbbd2e9bc36ee99cbd3448cbf2e6b548cefeaed
diff --git a/src/compiler/codegen/arm/ArchUtility.cc b/src/compiler/codegen/arm/ArchUtility.cc
index 52fb018..5e8fa20 100644
--- a/src/compiler/codegen/arm/ArchUtility.cc
+++ b/src/compiler/codegen/arm/ArchUtility.cc
@@ -455,7 +455,7 @@
 
     // Dump mapping table
     if (cUnit->mappingTable.size() > 0) {
-        std::string line(StringPrintf("\n    MappingTable %s%s_%s_mappingTable[%d] = {",
+        std::string line(StringPrintf("\n    MappingTable %s%s_%s_mappingTable[%zu] = {",
             descriptor.c_str(), name.c_str(), signature.c_str(), cUnit->mappingTable.size()));
         std::replace(line.begin(), line.end(), ';', '_');
         LOG(INFO) << line;