Add gmock into our dependencies.

third_party/boost/boost/config/compiler/greenhills.hpp

Index: third_party/boost/boost/config/compiler/greenhills.hpp
diff --git a/third_party/boost/boost/config/compiler/greenhills.hpp b/third_party/boost/boost/config/compiler/greenhills.hpp
new file mode 100644
index 0000000000000000000000000000000000000000..038b6b2b52e7b3dcd8bd9e9c1b310176262286a0
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+++ b/third_party/boost/boost/config/compiler/greenhills.hpp
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+//  (C) Copyright John Maddock 2001. 
+//  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.
+
+//  Greenhills C++ compiler setup:
+
+#define BOOST_COMPILER "Greenhills C++ version " BOOST_STRINGIZE(__ghs)
+
+#include "boost/config/compiler/common_edg.hpp"
+
+//
+// versions check:
+// we don't support Greenhills prior to version 0:
+#if __ghs < 0
+#  error "Compiler not supported or configured - please reconfigure"
+#endif
+//
+// last known and checked version is 0:
+#if (__ghs > 0)
+#  if defined(BOOST_ASSERT_CONFIG)
+#     error "Unknown compiler version - please run the configure tests and report the results"
+#  endif
+#endif
+
+