ci: add travis ci support for native aarch64

ci: add travis ci support for native aarch64

Add Travis compilation jobs for native aarch64. gcc/clang compilations
for static/shared libraries are added.

Some limitations for current aarch64 Travis support:
1. Container is used. Huge page is not available due to security reason.
2. Missing kernel header package in Xenial distribution.

Solutions to address the limitations:
1. Not to add unit test for now. And run tests with no-huge in future.
2. Use Bionic distribution for all aarch64 jobs.

Signed-off-by: Ruifeng Wang <ruifeng.wang@arm.com>
Reviewed-by: Gavin Hu <gavin.hu@arm.com>
Acked-by: Aaron Conole <aconole@redhat.com>