Fix build errors for macOS
PR <https://github.com/Genymobile/scrcpy/pull/1960>
// modern glibc will complain without this
#define _DEFAULT_SOURCE
+#ifdef __APPLE__
+# define _DARWIN_C_SOURCE // for strdup(), strtok_r(), memset_pattern4()
+#endif
+
#include "command.h"
#include "config.h"
