When configuring a Kit based on a "Docker Device", trying to configure a "CMake generator" of "Ninja" checks the local system for the ninja tool instead of checking in the docker image. It wrongly fails if ninja is missing locally but available in the docker image. And it probably wrongly succeeds if ninja is available locally but missing in the docker image (untested).

Looking at the code I think this might be CMakeGeneratorKitAspectFactory::fix(Kit *k) which calls CMakeGeneratorKitAspectFactory::isNinjaPresent(const Kit *k, const CMakeTool *tool) which performs a local filesystem search for a file ninja.