snappy build on macos will fail

[jacquesqiao]

the log is

cpplint: Checking source code style
Undefined symbols for architecture x86_64:
  "testing::InitGoogleTest(int*, char**)", referenced from:
      _main in snappy_unittest.cc.o
  "testing::AssertionResult::AssertionResult(testing::AssertionResult const&)", referenced from:
      testing::AssertionResult testing::internal::CmpHelperOpFailure<char, char>(char const*, char const*, char const&, char const&, char const*) in snappy_unittest.cc.o
      testing::AssertionResult testing::internal::CmpHelperOpFailure<int, unsigned short>(char const*, char const*, int const&, unsigned short const&, char const*) in snappy_unittest.cc.o
  "testing::AssertionFailure()", referenced from:
      testing::AssertionResult testing::internal::CmpHelperOpFailure<char, char>(char const*, char const*, char const&, char const&, char const*) in snappy_unittest.cc.o
      testing::AssertionResult testing::internal::CmpHelperOpFailure<int, unsigned short>(char const*, char const*, int const&, unsigned short const&, char const*) in snappy_unittest.cc.o
  "testing::AssertionSuccess()", referenced from:
      snappy::Snappy_FindMatchLength_Test::TestBody() in snappy_unittest.cc.o
      snappy::Snappy_FindMatchLengthRandom_Test::TestBody() in snappy_unittest.cc.o
      snappy::Snappy_VerifyCharTable_Test::TestBody() in snappy_unittest.cc.o
      testing::AssertionResult testing::internal::CmpHelperEQ<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >, std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > >(char const*, char const*, std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&, std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&) in snappy_unittest.cc.o
  "testing::Test::SetUp()", referenced from:
      vtable for snappy::CorruptedTest_VerifyCorrupted_Test in snappy_unittest.cc.o
      vtable for snappy::Snappy_SimpleTests_Test in snappy_unittest.cc.o
      vtable for snappy::Snappy_MaxBlowup_Test in[  9%] Linking CXX static library libenforce.a
 snappy_unittest.cc.o
      vtable for snappy::Snappy_RandomData_Test in snappy_unittest.cc.o
      vtable for snappy::Snappy_FourByteOffset_Test in snappy_unittest.cc.o
      vtable for snappy::Snappy_IOVecEdgeCases_Test in snappy_unittest.cc.o
      vtable for snappy::Snappy_IOVecLiteralOverflow_Test in snappy_unittest.cc.o
      ...
  "testing::Test::TearDown()", referenced from:
      vtable for snappy::CorruptedTest_VerifyCorrupted_Test in snappy_unittest.cc.o
      vtable for