ISO build from devel fails with mesa 12.0.3-1~bpo8+1

Build fails with “xorg : Depends: libgl1-mesa-dri but it is not going to be installed”, presumably since mesa 12.0.3-1~bpo8+1 was uploaded to jessie-backports.

Feature Branch: bugfix/11853-mesa-12.0.3

Related issues

Related to #11850 (closed)
Related to #11831 (closed)

Original created by @intrigeri on 11853 (Redmine)

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