libaria2 use xz to configure its source.
If we compile the xz tool, libaria2 will use the compiled binary.
However, on cross compilation, xz will be compiled for the target platform
and run on the host platform. And so, it will fails.
As we do not use those tools at all, lets not compile them.
Make kiwix-build installable using pip.
Module is now called `kiwixbuild` because `kiwix-build` is not a valid
python identifier.
Also split toolchains in separated directory.
Matthieu Gautier
mhutti1