[RFC] Switch back to plain .gitignore?

[joholl]

So far, I've only had problems with our .gitignore generation. There is always something which is not ignored properly. Also, so far I've mostly not fixed these problems since our git.mk is a pain to work with.

Therefore as an open question: do we want to switch back to a plain old .gitignore? I know it cannot do certain things but it might still be better than what we have now.

@AndreasFuchsTPM @JuergenReppSIT