Introduce also a "NeutralEnv", a build environment independent of the
targeted platform. All `Source` now build using the neutralEnv.
Most of toolchains are also using neutralEnv except android_ndk who is
specific to a platform.
As toolchain are neutral, platform specific environment variables are now
set by the platformInfo directly instead of the toolchain.
Those dependencies are used for bittorent and metalink.
For now, we don't support those features (we should in the future).
However, it seems that if development package are installed on the system,
libaria will try to link with libsqlite3 and libxml3 anyway.
We have to investigate this, but it breaks static build of kiwix-tools.
As we are not using those feature for now, let's just explicitly
compile libaria2 without sqlite3 and libxml2.
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
Chris Li
Pseudo