SignTool should not attempt to sign 0 length files

[mmitche]

• This issue is blocking
• This issue is causing unreasonable pain

0 length files exist in some cases (e.g. python packages). We should not attempt to sign any of these.

[missymessa]

@ellahathaway do you know which epic this should go in? We're thinking VMR, but not sure.

[ellahathaway]

Yes, I'll add it to the correct epic and project!

[ellahathaway]

T-Shirt Size: XS

I think that this is as simple as checking the size of the file when it gets passed to the configuration class as an item to sign & skipping it if it's 0.