deqp: hack to resolve clashes on project name in externals
in repo_set, a map is reversed as a short-cut to find the checkout directory for an external project. Different suites (deqp/vk and gl/gles) use different externals and upstream remotes, which creates a 1-to-many map that cannot be reversed.
To get CI working, correct this lookup in the caller. The mechanism needs to be re-written.