Watcom C++ doesn't have dirent.h (uses direct.h instead).

src/xpdev/dirwrap.h

@@ -147,7 +147,7 @@ extern "C" {
 	struct dirent  *	readdir  (DIR *__dir);
 	int                 closedir (DIR *__dir);
 	void                rewinddir(DIR *__dir);
-#else
+#elif !defined(__WATCOMC__)
 	#include <dirent.h>	/* POSIX directory functions */
 #endif