make: Conditionally link to the OSX Security framework.
diff --git a/ndn-cpp/security/identity/osx-private-key-storage.hpp b/ndn-cpp/security/identity/osx-private-key-storage.hpp
index 514d660..d206a04 100644
--- a/ndn-cpp/security/identity/osx-private-key-storage.hpp
+++ b/ndn-cpp/security/identity/osx-private-key-storage.hpp
@@ -8,10 +8,9 @@
 #ifndef NDN_OSX_PRIVATEKEY_STORAGE_H
 #define NDN_OSX_PRIVATEKEY_STORAGE_H
 
-// Only compile if ndn-cpp-config.h defines NDN_CPP_HAVE_OSX_SECKEYCHAIN 1.
+// Only compile if ndn-cpp-config.h defines NDN_CPP_HAVE_OSX_SECURITY 1.
 #include "../../ndn-cpp-config.h"
-#if 0 // temporarily disable.
-//#if NDN_CPP_HAVE_OSX_SECKEYCHAIN
+#if NDN_CPP_HAVE_OSX_SECURITY
 
 #include "../../common.hpp"
 #include "private-key-storage.hpp"
@@ -201,6 +200,6 @@
   
 }
 
-#endif NDN_CPP_HAVE_OSX_SECKEYCHAIN
+#endif NDN_CPP_HAVE_OSX_SECURITY
 
 #endif