Buck: Fix source path generation for JGit cell
Buck: Fix source path generation for JGit cell

Due to Buck bug: [1] root cell name is neither preserved nor resolved
in `buck audit classpath --dot` output and thus cannot be passed to
Buck again. Add a hack and help Buck for now until the bug is fixed.

* [1] https://github.com/facebook/buck/issues/656

Change-Id: I5973c1c7d81e51ba882c1f10658237a4c8e6a642

WANdisco/gerrit,gerrit-review/gerrit,qtproject/qtqa-gerrit,qtproject/qtqa-gerrit,MerritCR/merrit,joshuawilson/merrit,gerrit-review/gerrit,joshuawilson/merrit,GerritCodeReview/gerrit,gerrit-review/gerrit,joshuawilson/merrit,GerritCodeReview/gerrit,WANdisco/gerrit,qtproject/qtqa-gerrit,MerritCR/merrit,qtproject/qtqa-gerrit,MerritCR/merrit,joshuawilson/merrit,qtproject/qtqa-gerrit,WANdisco/gerrit,GerritCodeReview/gerrit,WANdisco/gerrit,joshuawilson/merrit,gerrit-review/gerrit,WANdisco/gerrit,gerrit-review/gerrit,joshuawilson/merrit,GerritCodeReview/gerrit,GerritCodeReview/gerrit,joshuawilson/merrit,GerritCodeReview/gerrit,GerritCodeReview/gerrit,gerrit-review/gerrit,joshuawilson/merrit,MerritCR/merrit,qtproject/qtqa-gerrit,GerritCodeReview/gerrit,qtproject/qtqa-gerrit,MerritCR/merrit,WANdisco/gerrit,MerritCR/merrit,WANdisco/gerrit,MerritCR/merrit,gerrit-review/gerrit,MerritCR/merrit