Bug 41325: Exclude Applications symlink when extracting dmg file in dmg2mar

Recent versions of 7z fail to extract our dmg files since the
`Applications` symlink points outside the archive:
https://sourceforge.net/p/sevenzip/discussion/45797/thread/9f5b067368/?page=1&limit=50#2c78

We exclude the `Applications` symlink to avoid the issue. We don't need
it since it is not included in the mar file.

tools/dmg2mar

@@ -132,6 +132,7 @@ sub convert_files {
         $pm->start($step_name) and next;
         my $tmpdir = File::Temp->newdir();
         my (undef, $err, $success) = capture_exec('7z', 'x', "-o$tmpdir",
+                                                        '-x!*/Applications',
                                                         $file->{filename});
         exit_error "Error extracting $file->{filename}: $err" unless $success;