enhance(ci): Use the default build chain on travis
enhance(ci): Use the default build chain on travis

Travis includes g++ and clang by default
https://docs.travis-ci.com/user/languages/c/

The ubuntu toolchain source is just used for gcc - the other packages are not
hosted there
https://launchpad.net/~ubuntu-toolchain-r/+archive/ubuntu/test

LN-Zap/zap-desktop,LN-Zap/zap-desktop,LN-Zap/zap-desktop