Fix generated script workflow

[seemikehack]

The generated clean script has several issues:

• it includes itself as a file to be cleaned, which is not documented
• it is generated with perms 544, meaning that when it tries to clean itself (as above), it doesn't do so silently, i.e., I have to approve the delete, which is annoying

Thoughts?

[srcreigh]

Seems reasonable---I'd take a PR to fix these issues