ansible: add gcc-8 to Ubuntu 18.04 hosts/containers

[richardlau]

Baseline gcc/g++ compiler version for Node.js 16 and above is 8. The
default gcc and g++ packages on Ubuntu 18.04 install version 7.

Moves gcc-6 and g++-6 out of the common ubuntu packages into
ubuntu1604 -- it doesn't seem worth installing a lower version of
GCC to the default for Ubuntu 18.04.

Update select-compiler.sh to select GCC 8 for Node.js 16 and later.

Refs: #2445

[richardlau]

FWIW I'm not convinced the containers created by ansible/roles/docker/templates/ubuntu1804.Dockerfile.j2 are actually being used in our CI.
i.e.

• https://ci.nodejs.org/computer/test-digitalocean-ubuntu1804_container-x64-1/builds
• https://ci.nodejs.org/computer/test-digitalocean-ubuntu1804_container-x64-2/builds
• https://ci.nodejs.org/computer/test-softlayer-ubuntu1804_container-x64-1/builds

are all empty (compare to an actual non-container e.g. https://ci.nodejs.org/computer/test-packetnet-ubuntu1804-x64-1/builds)

[rvagg]

yeah, probably not used, they were at one stage for some temporary testing work and they also exist as a way of experimenting with offloading VM tests to container tests, but other than that they're probably idling (which really only costs us the memory impact of the jenkins nodes)

[richardlau]

I haven't deployed this anywhere yet.

[rvagg]

maybe we should just remove g++,gcc from here too?

[rvagg]

What do you think about being more explicit? Remove g++ and gcc from both baselayout and the Dockerfiles, add in g++-6 and gcc-6 and make select-compiler.sh use those instead of YOLO plain gcc and g++? As long as select-compiler.sh is involved it should be fine then. I'm not sure if it is on the bare 18.04 VMs but we could easily do that if needed.

[richardlau]

Pushed ca9dcab to remove gcc/g++ and explicitly install gcc-6/g++-6 (in addition to gcc-8/g++-8). I think (based on a modified local copy of the sharedlibs Dockerfile) we still end up with the gcc/g++ package installed through some dependency chain.

[richardlau]

I've deployed this onto the Docker containers hosted on

• test-digitalocean-ubuntu1804_docker-x64-1
• test-digitalocean-ubuntu1804_docker-x64-2
• test-softlayer-ubuntu1804_docker-x64-1

and the two test non-containered Ubuntu 18.04 hosts:

• test-digitalocean-ubuntu1804-x64-1
• test-joyent-ubuntu1804-x64-1

I've also updated the node-test-commit-linux-containered job to call the select-compiler.sh script (https://github.com/nodejs/jenkins-config-test/commit/96bd09b15124cdfc9f985a947d94091b325d9287 and https://github.com/nodejs/jenkins-config-test/commit/741f1f8553e411adbea24acfbad8591d3003da67) in preparation for when this PR is merged (until then the builds fall through the existing select-compiler.sh script and default to gcc/g++). The node-test-commit-linux job is already calling select-compiler.sh.