Ensure temp directories are cleaned up.

Tux reported that on certain platforms File::Temp::tempdir(CLEANUP => 1) was
not cleaning up after itself properly.  Guarantee that this cleanup takes
place in and END block.

Thread:
https://www.nntp.perl.org/group/perl.perl5.porters/2018/04/msg250757.html

Author: jkeenan

dist/PathTools/t/cwd_enoent.t

@@ -47,4 +47,6 @@ foreach my $type (qw(regular perl)) {
 
 chdir $tmp or die "$tmp: $!";
 
+END { chdir $tmp; }
+
 1;