Solve CircleCI Build Environment everywhere

[victorb]

Currently, in many repositories, we're still using Ubuntu 12.04 in the CircleCI build environment. This environment works if you add some hacks in the circle.yml file, but with the current one we have (https://github.com/ipfs/ci-sync/blob/992f127d79012a262fb0895ad72ddab4b387ab5e/configs/circle.yml) you'll need to use Ubuntu 14.04 version.

Currently, there is no easy way of migrating the build environment, but instead we're required to manually navigate the CircleCI UI and change the setting there. There is no support for setting this in the circle.yml file, neither an API endpoint for changing this. I've also been in contact with the customer support from CircleCI and they can't help us with this.

If you do see a NSS >= 3.26 is required error in the browser tests in CircleCI, you'll have to change the Build Environment setting from 12.04 to 14.04. You can find the setting here (using libp2p/js-libp2p-crypto as a example) https://circleci.com/gh/libp2p/js-libp2p-crypto/edit#build-environment