message: Define DATE_API empty when building static lib on Windows
diff: @@ -100,6 +100,8 @@ static_assert(HAS_REMOTE_API == 0 ? AUTO_DOWNLOAD == 0 : true,
  #ifdef _WIN32
  # ifdef DATE_BUILD_DLL
  # define DATE_API __declspec(dllexport)
  +# elif defined(DATE_BUILD_LIB)
  +# define DATE_API
  # else
  # define DATE_API __declspec(dllimport)
  # endif
  