Is it possible to stop .sudo_as_admin_successful being created?

Based on the following section of the plugins/sudoers/sudoers.c source code file, it doesn't look like it's possible without recompiling sudo, undefining the USE_ADMIN_FLAG pre-processor macro.

Also, note that it's checking for group membership of both admin and sudo. I haven't checked the changelog, but I suspect the latter check was added when sudo became the default group for privileged users - perhaps the filename still refers to admin for compatibility.

1229 #ifdef USE_ADMIN_FLAG
1230 static int
1231 create_admin_success_flag(void)
1232 {
1233     struct stat statbuf;
1234     char flagfile[PATH_MAX];
1235     int len, fd = -1;
1236     debug_decl(create_admin_success_flag, SUDOERS_DEBUG_PLUGIN)
1237
1238     /* Check whether the user is in the admin group. */
1239     if (!user_in_group(sudo_user.pw, "admin") &&
1240         !user_in_group(sudo_user.pw, "sudo"))
1241         debug_return_int(true);
1242
1243     /* Build path to flag file. */
1244     len = snprintf(flagfile, sizeof(flagfile), "%s/.sudo_as_admin_successful",
1245         user_dir);
1246     if (len <= 0 || (size_t)len >= sizeof(flagfile))
1247         debug_return_int(false);
1248
1249     /* Create admin flag file if it doesn't already exist. */
1250     if (set_perms(PERM_USER)) {
1251         if (stat(flagfile, &statbuf) != 0) {
1252             fd = open(flagfile, O_CREAT|O_WRONLY|O_EXCL, 0644);
1253             if (fd != -1)
1254                 close(fd);
1255         }
1256         if (!restore_perms())
1257             debug_return_int(-1);
1258     }
1259     debug_return_int(fd != -1);
1260 }
1261 #else /* !USE_ADMIN_FLAG */
1262 static int
1263 create_admin_success_flag(void)
1264 {
1265     /* STUB */
1266     return true;
1267 }
1268 #endif /* USE_ADMIN_FLAG */

It looks like this issue is being dealt with right now: https://github.com/sudo-project/sudo/issues/56