make: Create include directory for make install to install headers.  Put ndn-cpp-config.h in include/ndn-cpp.
diff --git a/ndn-cpp/security/identity/osx-private-key-storage.cpp b/ndn-cpp/security/identity/osx-private-key-storage.cpp
index 2a58d85..5cca7ca 100644
--- a/ndn-cpp/security/identity/osx-private-key-storage.cpp
+++ b/ndn-cpp/security/identity/osx-private-key-storage.cpp
@@ -6,7 +6,7 @@
  */
 
 // Only compile if ndn-cpp-config.h defines NDN_CPP_HAVE_OSX_SECURITY 1.
-#include "../../ndn-cpp-config.h"
+#include <ndn-cpp/ndn-cpp-config.h>
 #if NDN_CPP_HAVE_OSX_SECURITY
 
 #include <fstream>