
`spack dev-build` would incorrectly set `keep_stage=True` for the entire DAG, including for non-dev specs, even though the dev specs have a DIYStage which never deletes sources.
`spack dev-build` would incorrectly set `keep_stage=True` for the entire DAG, including for non-dev specs, even though the dev specs have a DIYStage which never deletes sources.