Tweaks for ppc64le

[joepvd]

• Add extra aliases for postgres and mongodb, so these are not easily typo'd in the services list
• Start mongodb differently when the architecture is PPC64LE
• Detect architecture at the start of the build and store it as $TRAVIS_ARCH

[grooverdan]

looks good with the aliases.

TRAVIS_ARCH seems useful, I'd almost started to use TRAVIS_OS_NAME before this was linux normalised.

I'm looking to see what can be done to get a newer apt version for mongodb on ppc64le.

Note in x86_64 trusty that using apt to specify a later (4.0) mongodb version will still result in the base image 3.4.10 version running: https://travis-ci.org/grooverdan/travis-test/jobs/401564974

[grooverdan]

Seems I can grab the ppc64le 3.6 version bionic easy enough and with this change it should start: https://travis-ci.org/grooverdan/travis-test/jobs/402005365

[joepvd]

:thinking:

Maybe this would be a better solution?

sudo systemctl start mongodb || sudo systemctl start mongod

Would need some cosmetics, so it does not look so convoluted in the build log.

[grooverdan]

To go fully compatible more is needed. Probably something like the postgresql addon detecting if packages where specified in the apt plugin and the determining which service from that.

As it stands a base image may have either a mongo or distro package, which can be upgraded by the user to a later mongo or distro package.