Add gmock into our dependencies.

third_party/boost/boost/preprocessor/cat.hpp

Index: third_party/boost/boost/preprocessor/cat.hpp
diff --git a/third_party/boost/boost/preprocessor/cat.hpp b/third_party/boost/boost/preprocessor/cat.hpp
new file mode 100644
index 0000000000000000000000000000000000000000..b2a82c0691258efdd1b1dddd1ef0f006845d4961
--- /dev/null
+++ b/third_party/boost/boost/preprocessor/cat.hpp
@@ -0,0 +1,35 @@
+# /* Copyright (C) 2001
+#  * Housemarque Oy
+#  * http://www.housemarque.com
+#  *
+#  * Distributed under 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)
+#  */
+#
+# /* Revised by Paul Mensonides (2002) */
+#
+# /* See http://www.boost.org for most recent version. */
+#
+# ifndef BOOST_PREPROCESSOR_CAT_HPP
+# define BOOST_PREPROCESSOR_CAT_HPP
+#
+# include <boost/preprocessor/config/config.hpp>
+#
+# /* BOOST_PP_CAT */
+#
+# if ~BOOST_PP_CONFIG_FLAGS() & BOOST_PP_CONFIG_MWCC()
+#    define BOOST_PP_CAT(a, b) BOOST_PP_CAT_I(a, b)
+# else
+#    define BOOST_PP_CAT(a, b) BOOST_PP_CAT_OO((a, b))
+#    define BOOST_PP_CAT_OO(par) BOOST_PP_CAT_I ## par
+# endif
+#
+# if ~BOOST_PP_CONFIG_FLAGS() & BOOST_PP_CONFIG_MSVC()
+#    define BOOST_PP_CAT_I(a, b) a ## b
+# else
+#    define BOOST_PP_CAT_I(a, b) BOOST_PP_CAT_II(a ## b)
+#    define BOOST_PP_CAT_II(res) res
+# endif
+#
+# endif