The default archive.ubuntu.com round-robin can serve out-of-sync index
files mid-sync, which makes apt-get update fail with 'File has unexpected
size' errors and breaks the deb build job for everyone until the upstream
mirror catches up.
Rewrite the container's apt sources to point at us-west-2.ec2.archive.
ubuntu.com instead. The EC2 archive mirrors are Canonical-operated,
region-local to the runs-on instances, and sync aggressively, eliminating
the round-robin lottery as a CI failure mode.
Signed-off-by: Ramon Roche <mrpollo@gmail.com>
1ba562f400