fetch_sources: do not consider platform support when fetching
DependencyGraph drops projects that cannot be executed on the current version due to hardware support. This prevents unnecessary scheduling of components.
DependencyGraph is also used to build a list of source projects that must be fetched. It may be that the version on disk prior to fetching does not support the target components. After fetching, the version will be updated. For this use case, DependencyGraph must not consider platform support.