Remove HAVE_DIRENT_D_TYPE.

Only Windows doesn't have it, and we don't build atree for Windows.

Change-Id: Ib6e96be73340c36cdfcb3654ed540f690bf7550b
diff --git a/tools/atree/files.cpp b/tools/atree/files.cpp
index df3e987..d945f58 100644
--- a/tools/atree/files.cpp
+++ b/tools/atree/files.cpp
@@ -447,14 +447,7 @@
             continue;
         }
         string entry = path_append(path, ent->d_name);
-#ifdef HAVE_DIRENT_D_TYPE
-		bool is_directory = (ent->d_type == DT_DIR);
-#else
-	    // If dirent.d_type is missing, then use stat instead
-		struct stat stat_buf;
-		stat(entry.c_str(), &stat_buf);
-		bool is_directory = S_ISDIR(stat_buf.st_mode);
-#endif
+        bool is_directory = (ent->d_type == DT_DIR);
         add_more(entry, is_directory, rec, more);
         if (is_directory) {
             dirs.push_back(entry);