fixing wdt macos/oss build
fixing wdt macos/oss build

Summary:
fixing wdt macos/oss build
follow up from folly changes D2713511 and D2709231

without this diff:

  [2/55] Linking CXX shared library libfolly4wdt.dylib
  FAILED: : && /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/c++  -msse4.2 -O3 -DNDEBUG  -dynamiclib -Wl,-headerpad_max_install_names  -o libfolly4wdt.dylib -install_name rpath/libfolly4wdt.dylib   CMakeFiles/folly4wdt.dir/Users/ldemailly/devserver/fbsource/fbcode/folly/Conv.cpp.o   CMakeFiles/folly4wdt.dir/Users/ldemailly/devserver/fbsource/fbcode/folly/Demangle.cpp.o CMakeFiles/folly4wdt.dir/Users/ldemailly/devserver/fbsource/fbcode/folly/Checksum.cpp.o CMakeFiles/folly4wdt.dir/Users/ldemailly/devserver/fbsource/fbcode/folly/detail/ThreadLocalDetail.cpp.o CMakeFiles/folly4wdt.dir/Users/ldemailly/devserver/fbsource/fbcode/folly/detail/MallocImpl.cpp.o CMakeFiles/folly4wdt.dir/Users/ldemailly/devserver/fbsource/fbcode/folly/detail/FunctionalExcept.cpp.o   && :
  Undefined symbols for architecture x86_64:
    "google::LogMessage::stream()", referenced from:
        folly::threadlocal_detail::PthreadKeyUnregister::~PthreadKeyUnregister() in ThreadLocalDetail.cpp.o
    "google::LogMessageFatal::LogMessageFatal(char const*, int)", referenced from:
        folly::threadlocal_detail::PthreadKeyUnregister::~PthreadKeyUnregister() in ThreadLocalDetail.cpp.o
    "google::LogMessageFatal::~LogMessageFatal()", referenced from:
        folly::threadlocal_detail::PthreadKeyUnregister::~PthreadKeyUnregister() in ThreadLocalDetail.cpp.o
  ld: symbol(s) not found for architecture x86_64

with it - it compiles, links and works

Reviewed By: ypisetsky

Differential Revision: D2717201

fb-gh-sync-id: 2e0e3d01fd63ff067d7616d80816b3724c152987

ldemailly/wdt,ldemailly/wdt,luluandleilei/wdt,luluandleilei/wdt,ldemailly/wdt,luluandleilei/wdt,ldemailly/wdt,luluandleilei/wdt