Add a compile-time constant bool equivalent to !defined(NDEBUG).

This makes some code slightly less awkward.

Change-Id: Iafd359dd0baa65510ed9510a7d93ee01605f51e4
diff --git a/src/heap.cc b/src/heap.cc
index d847682..f351b72 100644
--- a/src/heap.cc
+++ b/src/heap.cc
@@ -62,10 +62,7 @@
   std::vector<char*> arg_vector;
 
   std::string dex2oat_string(GetAndroidRoot());
-  dex2oat_string += "/bin/dex2oat";
-#ifndef NDEBUG
-  dex2oat_string += 'd';
-#endif
+  dex2oat_string += (kIsDebugBuild ? "/bin/dex2oatd" : "/bin/dex2oat");
   const char* dex2oat = dex2oat_string.c_str();
   arg_vector.push_back(strdup(dex2oat));