I should add that the core, non-Qt bits (i.e., the actual compiler setup) is based on the work done around the
KOReader toolchains.
And that I stand by the comment made about the nickel TC there: if you don't need to work with Nickel/Qt (eventually, the kernel), and if, where C++ is concerned, linking against the STL statically is not an issue, prefer the "kobo" toolchain target, because it uses a much more recent GCC version than the crapfest that is GCC 4.9

.
As an example, I don't actually use the nickel TC anywhere else than for NickelMenu. KOReader, KFMon, FBInk, KoboStuff are all built with the "kobo" TC.
If, for some reason (e.g., modern C++), you absolutely need a bleeding-edge compiler, that's also possible (i.e., I regularly run tests with the latest Clang & GCC versions), ping me, as that's slightly less user-friendly

.