Show signtool output on error

[mjerde]

The signtool output is captured but only displayed in the event of success. This makes it hard to identify the causes of signtool problems, especially since signtool is operating on files in a temp location which are cleaned up after failure. Adding output of the signtool output on error helped me identify the cause of a problem I had when trying to releasify.

Thank you, Squirrel team!

[caesay]

This has been fixed (along with several other signing related issues) in my fork here.

[mjerde]

Closed due to lack of traction.