add boost on mac

macx64/include/boost/contract/detail/debug.hpp

@@ -0,0 +1,20 @@
+
+#ifndef BOOST_CONTRACT_DETAIL_DEBUG_HPP_
+#define BOOST_CONTRACT_DETAIL_DEBUG_HPP_
+
+// Copyright (C) 2008-2018 Lorenzo Caminiti
+// Distributed under the Boost Software License, Version 1.0 (see accompanying
+// file LICENSE_1_0.txt or a copy at http://www.boost.org/LICENSE_1_0.txt).
+// See: http://www.boost.org/doc/libs/release/libs/contract/doc/html/index.html
+
+// Usually, never #defined (so "debug" assertions always in code).
+#ifdef BOOST_CONTRACT_DETAIL_NDEBUG
+    #define BOOST_CONTRACT_DETAIL_DEBUG(cond) /* nothing */
+#else
+    #include <boost/assert.hpp>
+    // Extra parenthesis around BOOST_ASSERT to be safe because its is a macro.
+    #define BOOST_CONTRACT_DETAIL_DEBUG(cond) (BOOST_ASSERT(cond))
+#endif
+
+#endif // #include guard
+