Add gmock into our dependencies.

third_party/boost/boost/config/compiler/gcc_xml.hpp

Index: third_party/boost/boost/config/compiler/gcc_xml.hpp
diff --git a/third_party/boost/boost/config/compiler/gcc_xml.hpp b/third_party/boost/boost/config/compiler/gcc_xml.hpp
new file mode 100644
index 0000000000000000000000000000000000000000..5dd67c760402aa46a30ff5fbf628e71ca0e3a7c0
--- /dev/null
+++ b/third_party/boost/boost/config/compiler/gcc_xml.hpp
@@ -0,0 +1,30 @@
+//  (C) Copyright John Maddock 2006. 
+//  Use, modification and distribution are subject to the 
+//  Boost Software License, Version 1.0. (See accompanying file 
+//  LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+
+//  See http://www.boost.org for most recent version.
+
+//  GCC-XML C++ compiler setup:
+
+#  if !defined(__GCCXML_GNUC__) || ((__GCCXML_GNUC__ <= 3) && (__GCCXML_GNUC_MINOR__ <= 3))
+#     define BOOST_NO_IS_ABSTRACT
+#  endif
+
+//
+// Threading support: Turn this on unconditionally here (except for
+// those platforms where we can know for sure). It will get turned off again
+// later if no threading API is detected.
+//
+#if !defined(__MINGW32__) && !defined(_MSC_VER) && !defined(linux) && !defined(__linux) && !defined(__linux__)
+# define BOOST_HAS_THREADS
+#endif 
+
+//
+// gcc has "long long"
+//
+#define BOOST_HAS_LONG_LONG
+
+#define BOOST_COMPILER "GCC-XML C++ version " __GCCXML__
+
+