mkisofs switch to joliet-long

[Smithx10]

Was adding long directories from Windows cab files and ran into an issue where mkisofs failed with just -joliet.

mkisofs has an -joliet-long which solved the problem.

We should either make this available via a config, or just default to long.

[rgl]

@Smithx10 try with xorriso (if found in path, packer will prefer it). maybe it works.

[Smithx10]

Am on an operating system that doesn't have xorriso packaged, So I was hoping we could add either switch or add an option.