add flag fail_on_non_hdl_files to vivado.py

[smenzel]

Fix https://github.com/VUnit/vunit/issues/782 as suggested by @LarsAsplund

[eine]

@smenzel, please check the format and linter errors.

[smenzel]

I fixed 3 of the linting issues, however, I don't know how to fix this problem without changing unrelated code that I don't understand fully: vunit/vivado/vivado.py:16:0: R0914: Too many local variables (16/15) (too-many-locals)

Also is it better to make a new commit for these review/linting changes or should I amend the previous commit (and force push in my branch) for a cleaner history?