fixup armv6l recipes

[richardlau]

Add the renamed armv6l-pre16 recipe to the explicit recipe list to build.

Add missing dependency (python3-distutils) for the new armv6l recipe to fix

ModuleNotFoundError: No module named 'distutils.spawn'

error. FWIW in https://github.com/nodejs/build/blob/master/ansible/roles/docker/templates/ubuntu1804_arm_cross.Dockerfile.j2 python3-distutils is installed as a dependency of python3-pip -- we do not need to install pip on the unofficial build Docker image as we're not running tap2junit here.

Refs: #33

[richardlau]

mea culpa for some reason I thought the scripts would just enumerate over the directories in recipes (like we do for building images

unofficial-builds/bin/prepare-images.sh

Lines 8 to 10 in 0d49da5

	for recipe in $(ls ${__dirname}/../recipes/); do
	docker build ${__dirname}/../recipes/${recipe}/ -t ${image_tag_pfx}${recipe}
	done

) but there's an explicit list in

unofficial-builds/bin/build.sh

Lines 11 to 17 in 0d49da5

	recipes=" \
	headers \
	x86 \
	musl \
	armv6l \
	x64-pointer-compression \
	x64-usdt \

.

FWIW The next release pre16 we have planned is next Tuesday (14.17.0, delayed for a week nodejs/node#38507 (comment)).

[rvagg]

btw the reason for the explicit list is that we need to run fetch separately and not have it included in this phase, but also that there's a sense of importance to the builds and because they're queued it's good to get the more important ones out first (although I don't recall whether we ended up with a "publish what's available" system or wait until they're all built - I'm also surprised that musl is not straight after headers since it's arguably much more important to get done ASAP).