The tar archives generated by gitian are currently unversioned. This
adds either a tag name when building from a tag, or a short commit id
when building from a commit hash.
Windows is built with a seperate descriptor to handle additional changes
that need to be done to the end binary. Consolidate the gitian-build
script for this change.
This adds a build script to run gitian builds for linux.
The build script was copied from bitcoin and then adapted for monero.
Build step documentation is outlined in the README in the contrib/gitian
directory.
