plugin: Ignore directories in the plugin-directory

They pass the executable test, but aren't really executable.

Signed-off-by: Christian Decker <decker.christian@gmail.com>

lightningd/plugin.c

@@ -664,7 +664,11 @@ static const char *plugin_fullpath(const tal_t *ctx, const char *dir,
 	fullname = path_join(ctx, dir, basename);
 	if (stat(fullname, &st) != 0)
 		return tal_free(fullname);
-	if (!(st.st_mode & (S_IXUSR|S_IXGRP|S_IXOTH)))
+	if (!(st.st_mode & (S_IXUSR|S_IXGRP|S_IXOTH)) || st.st_mode & S_IFDIR)
+		return tal_free(fullname);
+
+	/* Ignore directories, they have exec mode, but aren't executable. */
+	if (st.st_mode & S_IFDIR)
 		return tal_free(fullname);
 	return fullname;
 }