Update MentOs code to the latest development version.

programs/rmdir.c

@@ -0,0 +1,31 @@
+///                MentOS, The Mentoring Operating system project
+/// @file rmdir.c
+/// @brief
+/// @copyright (c) 2014-2021 This file is distributed under the MIT License.
+/// See LICENSE.md for details.
+
+#include <stdio.h>
+#include <string.h>
+#include <sys/stat.h>
+#include <strerror.h>
+
+int main(int argc, char *argv[])
+{
+    // Check the number of arguments.
+    if (argc != 2) {
+        printf("Bad usage.\n");
+        printf("Try 'rmdir --help' for more information.\n");
+        return 1;
+    }
+    if (strcmp(argv[1], "--help") == 0) {
+        printf("Removes a directory.\n");
+        printf("Usage:\n");
+        printf("    rmdir <directory>\n");
+        return 0;
+    }
+    if (rmdir(argv[1]) == -1) {
+        printf("%s: failed to remove '%s': %s\n\n", argv[0], argv[1], strerror(errno));
+        return 1;
+    }
+    return 0;
+}