rmdir: throw an error if operation fails and nargout == 0 (bug #57830). * dirfns.cc (Frmdir): Change DEFMETHODX macro invocation to include nargout variable. Check nargout, and for cases where "nargout == 0" and "status" indicates failure, throw an error. For cases where "nargout > 0", return 3-value octave_value_list in variable "retval". * file-io.cc, gzip.cc, dir.m, isfolder.m, mkdir.m, run.m, tar.m, unpack.m, zip.m, pathdef.m, savepath.m, configure_make.m, install.m, uninstall.m, getpref.m, setpref.m, pkg.tst, publish.tst, system.tst: Change calls from "rmdir" to "sts = rmdir" so that an error is not unecessarily thrown in BIST tests and other clean up code.

--- a/scripts/miscellaneous/unpack.m	Mon Feb 17 20:02:10 2020 -0800
+++ b/scripts/miscellaneous/unpack.m	Mon Feb 17 20:02:18 2020 -0800
@@ -372,7 +372,7 @@
 %!     unlink (filename);
 %!     unlink ([filename ".orig"]);
 %!     confirm_recursive_rmdir (false, "local");
-%!     rmdir (dirname, "s");
+%!     sts = rmdir (dirname, "s");
 %!   end_unwind_protect
 %! unwind_protect_cleanup
 %!   ## Restore environment variables TMPDIR, TMP