Building with docker is arguably easier and more familiar to most people
than either kvm, or lxc.
This commit also relaxes the back compat requirement a bit. 32 bit linux
now uses glibc version 2.0. Also, the docker shell could not handle gcc arguments
containing spaces, so the explicit '-DFELT_TYPE' declaration was dropped.
Lastly, this removes some packages from the osx descriptor.
The version prefix 'v' should just be set constantly.
Reflect this change in the README as well.
This should allow building commits as well, if a commit
is passed in instead of a tag.
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.
