message: Fix build on Windows with SDK build version >= 17134.
  Platform.h doesn't define signal() and SIGINT since commit r263858. Code was compiled successfully because signal.h didn't have "ifndef" include guard in previous versions of Windows SDK. Now it does.
diff: // MICmdBase.h / .cpp
  // MICmdCmd.h / .cpp
  -#if defined(_MSC_VER)
  -#define _INC_SIGNAL // Stop window's signal.h being included -
  - // CODETAG_IOR_SIGNALS
  -#endif // _MSC_VER
  -
  // Third party headers:
  #include "lldb/API/SBHostOS.h"
  #include <atomic>
  