`__COMPONENT_TARGETS` is evaluated very early when components and
component directories are added to the build, which means that all
components (including the ones which are in EXCLUDE_COMPONENTS) have
a build system target defined. The component manager was given the
list of all known components (derived from the list of targets), not
the list of components after EXCLUDE_COMPONENTS were processed.
Because of that, EXCLUDE_COMPONENTS didn't effectively exclude the
component from the consideration of the component manager.