I'm pretty sure it's not actually failing on the docs (mine are never installed), but rather a silent library check right after the doc check. There are a couple of extra libraries that the configure script is expecting that aren't actually checked for (or otherwise mentioned). I think if you make sure that libxext-dev and libx11-dev are installed, it should configure without disabling qt validation. I've been meaning to tweak the configure scripts to either explicitly check for the presence of those libs, or remove the dependency if it's no longer needed. But unfortunately I haven't had time lately.