Travis-ci: added support for ppc64le

[sanjaymsh]

Hi,
I have added support for ppc64le build on travis-ci in the branch . The travis-ci build log can be tracked on the link :https://travis-ci.com/github/sanjaymsh/fscrypt/builds/190125651 . I believe it is ready for the final review and merge.
Please have a look on it and if everything looks fine for you then please approve it for merge.

Thanks !!

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[sanjaymsh]

@googlebot I signed it!