Xenial and cache support added for ARM builds

Additionally to Ubuntu Bionic 18.04, Ubuntu Xenial 16.04 is now available to run ARM builds. Ubuntu Xenial 16.04 is now the default image (if you don't specify a dist:' in your .travis.yml Xenial will start automatically.)

Other changes:

  • Added ruby language for Xenial and Bionic distributions,
  • Added C lang for Xenial
  • Added minimal images for Xenial and Bionic
  • Increased disk size for LXD containers on ARM architecture to approx. 18GB
  • added support for cache and workspace for builds run within LXD containers on ARM infrastructure

To enable testing on multiple CPU architectures, just add the arch: key to your .travis.yml:

arch:
  - amd64
  - arm64
os: linux  # different CPU architectures are only supported on Linux

You can learn more in the multi-CPU architecture support announcement and in the multi-CPU architectures docs.