Adding power support to Travis builds

[ghatwala]

As we all know Travis officially supports multiple arch's now - https://blog.travis-ci.com/2019-11-12-multi-cpu-architecture-ibm-power-ibm-z .
Adding support for "ppc64le" arch for this repo with below changes ..

1. Installing moonjit in place of luajit for power
2. Using gcc-7, g++-7 compiler as default during builds for power
3. Avoiding installing gcc-4.8 for power
4. Adding power support in travis.yml

sysdig-CLA-1.0-contributing-entity: IBM
sysdig-CLA-1.0-signed-off-by: Amit Ghatwal ghatwala@us.ibm.com

[nathan-b]

Hi @ghatwala . When I look at the travis results for this PR, I don't see the ppc64le run. Where can I check to verify that it's running correctly?

[edmondsw]

@nathan-b I see ppc64le in the Travis results. If you click on the Details link for the Travic CI - Pull Request check, you should see 6 jobs were run (2 for x86 linux, 2 for osx, and 2 for ppc64le linux) instead of just 4. The last two of those are the new ppc64le jobs. E.g. https://travis-ci.com/draios/sysdig/jobs/268086746

[nathan-b]

@edmondsw thanks, I thought I clicked through all the Linux builds and saw AMD64, but I must have clicked on the same ones twice. Looks good, thanks!

[ghatwala]

Thanks @nathan-b and @edmondsw !!!