conan has very strict requirements on the versions of its dependencies.
This patch adds downgraded versinos of node-semver and distro to
statisfy these requirements.
This makes the HTML-docs an default-off option. Inline documentation
(`matrix-plot??`) is still available and HTML docs are available online.
Motivation: Get below the Hydra output size limit.
The build was failing on some machines because of a `find` command that
touched files in different orders on different machines.
That confused `make`s timestamp mechanism.
The sandboxed build was failing, because it relied heavily on
/usr/bin/env. This is fixed with a lot of shebang patching (both
to system packages and to sage-internal packages).
This "un-breaks" sage while also updating it to 8.0.
It compiles sage with its dependencies as one big pile, which is not
the best approach but definately better than nothing for now.
To be able to shrink the huge output pile a little, it also splits
docs from the rest of the output.
Timo Kaufmann