Kconfig.dep depends on FORCE, so it is always generated when compiling
with Kconfig under normal conditions. Whan TEST_KCONFIG=1 is set, this
file is no longer a dependency for out.config. So when cleaning the
'bin' directory, out.config has no direct dependencies that force its
rebuilding (the generated directory is order only). This causes the file
not to be produced when calling `TEST_KCONFIG=1 make clean all`.
This PR changes the dependency on the 'generated' directory to a direct
dependency when `CLEAN` is set and leaves it as order-only when not.
This allows to generate out.config only when needed by not depending on
FORCE.
4fbbb94bff