Fix CVE-2018-12015:

https://security-tracker.debian.org/tracker/CVE-2018-12015
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2018-12015
https://rt.cpan.org/Ticket/Display.html?id=125523

Patch taken from this upstream commit and adapted to apply to
the bundled copy in the Perl distribution:

https://github.com/jib/archive-tar-new/commit/ae65651eab053fc6dc4590dbb863a268215c1fc5

diff --git a/cpan/Archive-Tar/lib/Archive/Tar.pm b/cpan/Archive-Tar/lib/Archive/Tar.pm
index 6244369..a83975f 100644
--- a/cpan/Archive-Tar/lib/Archive/Tar.pm
+++ b/cpan/Archive-Tar/lib/Archive/Tar.pm
@@ -845,6 +845,20 @@ sub _extract_file {
         return;
     }
 
+    ### If a file system already contains a block device with the same name as
+    ### the being extracted regular file, we would write the file's content
+    ### to the block device. So remove the existing file (block device) now.
+    ### If an archive contains multiple same-named entries, the last one
+    ### should replace the previous ones. So remove the old file now.
+    ### If the old entry is a symlink to a file outside of the CWD, the new
+    ### entry would create a file there. This is CVE-2018-12015
+    ### <https://rt.cpan.org/Ticket/Display.html?id=125523>.
+    if (-l $full || -e _) {
+	if (!unlink $full) {
+	    $self->_error( qq[Could not remove old file '$full': $!] );
+	    return;
+	}
+    }
     if( length $entry->type && $entry->is_file ) {
         my $fh = IO::File->new;
         $fh->open( $full, '>' ) or (