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/dir.m	Mon Feb 17 20:02:10 2020 -0800
+++ b/scripts/miscellaneous/dir.m	Mon Feb 17 20:02:18 2020 -0800
@@ -224,7 +224,7 @@
 %!   chdir (orig_dir);
 %!   confirm_recursive_rmdir (false, "local");
 %!   if (exist (tmp_dir))
-%!     rmdir (tmp_dir, "s");
+%!     sts = rmdir (tmp_dir, "s");
 %!   endif
 %! end_unwind_protect
 
@@ -238,7 +238,7 @@
 %!   assert (list(1).folder, canonicalize_file_name (tmp_dir));
 %! unwind_protect_cleanup
 %!   if (exist (tmp_dir))
-%!     rmdir (tmp_dir);
+%!     sts = rmdir (tmp_dir);
 %!   endif
 %! end_unwind_protect