CircleCI Linux automatic builds

[DanielUranga]

Initial CircleCI support. Builds using Ubuntu Linux 18.04.
Build log here: https://circleci.com/gh/DanielUranga/lc0/10
This is an attempt to start solving #50

[DanielUranga]

Example lc0 Ubuntu 18.04 autogenerated binary: https://15-138075467-gh.circle-artifacts.com/0/lc0-ubuntu-18-04

[DanielUranga]

I think this is ready to merge now. It builds using both g++ and clang with every dependency but "Accelerate" and uploads the generated binaries.

[mooskagh]

I have no idea what's all that about, but as that's in a separate directory, fine to merge.

[dubslow]

I'll take a closer look then and merge it within a day or two.

Here are some binaries, for reference:

[3:05 PM] fersbery: builds using both g++ and clang, and uploads both binaries
[3:06 PM] fersbery: https://24-138075467-gh.circle-artifacts.com/0/lc0-ubuntu-18-04-clang
[3:06 PM] fersbery: and
[3:06 PM] fersbery: https://24-138075467-gh.circle-artifacts.com/0/lc0-ubuntu-18-04-g%2B%2B

[DanielUranga]

After this gets merged, the Leela organization will need to create an account on CircleCI and configure it for automatic builds (can be configured for every branch and for PRs), and it is possible to also display status badges.

[DanielUranga]

Also it should be possible to use something like Ghr (https://github.com/tcnksm/ghr) to automatically upload Github releases.

[mooskagh]

@DanielUranga I'm not sure how that works in github, but I think that after PR has an approval, you should have "Merge" button available. If you don't have that, I can merge. (also it would be nice to know whether it's indeed to)

[DanielUranga]

Nope, I can't merge: Only those with write access to this repository can merge pull requests.