Since libc++ is already used on Mac OSX, it would be nice to support it on Linux too (at least for x86 and x86_64). Linux library is already up to par with Mac OSX one. All other components already support building with clang/libc++.
Currently, when I build qtbase with -platform linux-clang-libc++, I get the following when trying to run qmake for qtwebengine module:
Qt WebEngine can currently only be built for Linux (GCC/clang), Windows (MSVC 2013 or 2015), OS X (10.9/XCode 5.1+) or Qt for Device Creation.
QtWebEngine will not be built