Ninja: Remove CMake includes from explicit depends (#14972)

It may happen that CMake include is an explicit dependency for some command,
while all CMake includes are set phony in WriteTargetRebuildManifest, this may
lead to duplicate phony generate rules which causes ninja warnings.

We need to remove implicit CMake includes in WriteUnknownExplicitDependencies.

This fixes FindCUDA ninja warnings.
Merge topic 'ninja-avoid-double-phony' into next

04377f1b Ninja: Remove CMake includes from explicit depends (#14972)