Not that I can help with your compilation issues, but I can explain the justification for no 14.04 support. Basically, uBuntu have only released 14.04 really recently, and when you download it, it says it is partially experimental, and may well be buggy, whereas 13.x is the release that they suggest using if you want a completely usable OS. Basically, that means that 14.04 users are a minority right now, and it crashes. I've got it on a netbook, and can confirm it crashes (although it usually just hangs for a minute and then comes up with a dialogue saying it recovered from a critical error, as opposed to just shutting down). This means that 13.x is the better version to support, as it's got a wider user base, and won't break Dolphin as much. Give it time for uBuntu themselves to recommend 14.04 as the safest, and I'm sure Dolphin will provide builds by then. If enough people want it, it may even be possible to have both, as the buildbot has more free time since 32-bit support has been dropped.
OS: Windows 10 64 bit Professional
CPU: AMD Ryzen 5900X
RAM: 16GB
GPU: Radeon Vega 56
CPU: AMD Ryzen 5900X
RAM: 16GB
GPU: Radeon Vega 56
