Set release to 999 for released commits

If the commit being built is a released version we need to
make sure the delorean release version is high enough to take
preference over the distro (which may have a higher release number).

Change-Id: I7e98e6ed65dc32492b04030ed2d94bbcd01f4e7f
Install gcc in build image

gcc is required to build some packages but isn't required in the spec
file so have it preinstalled.

Change-Id: I9132f8572f61e8bdaae62f7fc41b6fc29ad615e7