Now that issues associated with this bump have been addressed
elsewhere, reinstate trusty as the default DIB_RELEASE for
the ubuntu element. Also adds a note about memory requirements
to the ramdisk element.
Change-Id: Ia89c83ba0ee4ad3bd89b833ba0db08135eac63ed
Ramdisks are now built inside a chroot which is built by the normal
image build process. Doing so improves our independence of the
precise state of the build host.
This fixes bug 1194055.
Change-Id: Ibc254fbb9e7b404b5f38c1b35bcde8a4136e8e28
