Add Zephyr smp_svr build testing to Travis-CI

[utzig]

This builds smp_svr directly from the Zephyr tree; the purpose is to assure that the provided sample is still in a good build state when the mcumgr code changes.

[utzig]

This takes an approach as suggested by #60 (comment). Instead of having multiple copies that need to be constantly synchronized (Possible losing commit history), allow the sample to live outside the tree and check that it is in a build state here.

Would be easy to add Mynewt build testing as well, so maybe, smp_svr for Mynewt could live in the core repo (eg apps/smp_svr) and we could leave here just a non-functional sample with OS specific stuff as "to implement" comments or something similar.

There are no tests running as of now, only building the app!

/cc @vrahane @mlaz @nvlsianpu @carlescufi @de-nordic

[utzig]

Well, no comments so I am assuming this was not a good idea. I will add reviewers because it might still be considered helpful to have this build on CI, otherwise feel free to close the PR and let's move on with #60 or #62.

[vrahane]

Hi @utzig we haven’t closed the loop yet on whether we will keep the smp_svr in mcumgr upstream for zephyr as is or just keep the zephyr version of it. So, I would suggest adding builds for both the zephyr version as well as the upstream version for now atleast until we come to a consensus.

[carlescufi]

I am very skeptical of this. It is not going to be possible to maintain master:master compatibility between this repo and zephyrproject-rtos/zephyr, there is gonna be failures.

[carlescufi]

If you are going to use Zephyr, you really should use west to pull down the repos. How else are you going to be sure that you are pulling the right set?