This makes the Linux GN builds use the Chromium copy of binutils and
also makes all platforms use the "custom libcxx" which is libc++.
We do this so that the build doesn't depend on anything from the system
on Linux because our bots are still on trusty with very old libstdc++
and linkers.
Change-Id: I0570fb474f2945c3565e78a56aba66c1a2619afc
This makes the Jinja2 (and MarkupSafe) installation hermetic by
adding it to the DEPS and making the code generator add them in the
first spot of the python path.
Corentin Wallez