Ninja: Windows10 Filename longer than 260 characters

After updating from cmake-3.19.1 to cmake-3.21.0 a build broke that used to work with cmake-3.19.1. The path is indeed longer than 260 characters. But that worked before updating cmake.

Update:

I tried cmake-3.20.5 and that worked. I don't know if that is important, but I install cmake via chocolatey.