Fix out-of-tree builds
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This merge request is automatically cherrypicked from !1831 (merged) from source branch https://source.coderefinery.org/andrii/arc/-/tree/out-of-tree-build-fix orginally made by @andrii .
The original MR went to branch: https://source.coderefinery.org/nordugrid/arc/-/tree/next
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Adding explicit source tree path to the files missing it and blocking out-of-tree builds.