This allows us to use it to setup the gcc host compiler for the Windows
build in projects/firefox/build.

And buildconf/nb_procs to buildconf/num_procs.

We bump our GCC compiler to 5.4.0 as this fixes some bugs
in previous versions. It allows us in particular to build
debug builds for Windows with mingw-w64.

tor-browser-bundle.git author: Georg Koppen <gk@torproject.org>

ESR52 includes this commit:
https://hg.mozilla.org/mozilla-central/rev/f8cf0fe7c810
which changes the compiler used from 'c++' to 'g++'.

tor-browser-bundle.git commit: 48b68f84b34aef3567aeffe6932ff1e40d900f2b

Only for linux-x86_64 for now, as it fails to build on linux-i686.

To be closer to what we currently have in gitian, use binutils 2.24.

We also change tho OS to Ubuntu 12.04 for Windows builds, except for the
tor-browser bundle step, where we are staying with 14.10. We are using
14.10 in the tor-browser step because the version of python-pefile we
use fails on Ubuntu 12.04. The reason for using a recent version of
python-pefile is that the older versions don't work on x86_64. And we
are using an x86_64 container because docker does not support i386
containers. The problem is not present in gitian where we are using an
i386 VM. An other possible solution could be to build a recent version
of python.

Copy components from tor-messenger-build that will be useful for
building Tor Browser.

Copied from tor-messenger-build.git at commit f6411d2a66dae17e09e.