I'm not aware of what could be done on the Qt side, as it's related to the 14.04.X LTS HWE upgrades where X >= 2. The upgrade is complex and some of the mesa packages have seen slight changes (in addition to being just -lts-vivid suffixed).
It's not as qtbase5-dev could not be installed as such, it's that apt needs to be hinted additionally with eg that libgles2-mesa-dev for the install to succeed. So apt could handle the situation better, or something could maybe improved in the HWE packages.
I'm not aware of what could be done on the Qt side, as it's related to the 14.04.X LTS HWE upgrades where X >= 2. The upgrade is complex and some of the mesa packages have seen slight changes (in addition to being just -lts-vivid suffixed).
It's not as qtbase5-dev could not be installed as such, it's that apt needs to be hinted additionally with eg that libgles2-mesa-dev for the install to succeed. So apt could handle the situation better, or something could maybe improved in the HWE packages.