Ability to ignore paths that may or may not be present

[Wirone]

As described here, update to 1.11.9 is not possible without changes in our setup. I am not saying it's impossible to do, I just wanted to ask if that change was conscious, as it looks kinda like breaking change.

In our case, utils/phpstan/baseline-full.php may or may not be present when analysis is done. This file is a product of baseline generation, but is ignored in our repo because our CLI command splits it into area-scoped baselines and generates the file that is included in the main config (generated file itself contains includes of all area-scoped baselines, generated from the full baseline).

I can extend our CLI command to remove this intermediary file after it's split, and remove the entry from excludePaths, but I am not sure if it should be needed at all. I think the ability to ignore files that are not part of the repo (developer-specific files, environment-specific files) was helpful, and in the 1.11.9 it causes unnecessary (IMHO) errors.

[ondrejmirtes]

Please follow #11436.