Output files obstruct build

[stefanches7]

Environment

linux, anaconda, sm 5.3.0, wB 1.2.0

Issue description

When the Output/all.done, Output/html/index.html and Output/html/readme.html are there, system doesn't react to addition of new scripts.

Steps to reproduce the issue

1. Build project fully (until all.done step)
2. Add new script

What's the expected result?

New script gets compiled and added to index

What's the actual result?

Nothing to be done message from snakemake