Enable -Wthread-safety for Clang and CMake. (#1403)
Enable -Wthread-safety for Clang and CMake. (#1403)

https://cmake.org/cmake/help/v3.2/variable/CMAKE_LANG_COMPILER_ID.html
larics/cartographer,damonkohler/cartographer,cartographer-project/cartographer,wohe/cartographer,larics/cartographer,larics/cartographer,googlecartographer/cartographer,damonkohler/cartographer,cartographer-project/cartographer,wohe/cartographer,cartographer-project/cartographer,cartographer-project/cartographer,wohe/cartographer,larics/cartographer,damonkohler/cartographer,googlecartographer/cartographer,damonkohler/cartographer,wohe/cartographer,googlecartographer/cartographer,googlecartographer/cartographer