Support Alpine Linux & OpenRC

[tomalok]

Issue #, if available:
Resolves #50

Description of changes:
Adds support for Alpine Linux / OpenRC

[tomalok]

@Cappuccinuo i've been running with this patch on Alpine for some time now -- would be great if this got merged... ;)

[Cappuccinuo]

Thanks @tomalok for the PR, we'll find someone to work on this. Can you provide the AMI you are using?

[Cappuccinuo]

LGTM in general. Minor comments.

[tomalok]

Thanks @tomalok for the PR, we'll find someone to work on this. Can you provide the AMI you are using?

Previously I was applying the patch as a customization on top of https://gitlab.alpinelinux.org/alpine/cloud/alpine-ec2-ami, which until recently was building the official Alpine Linux AMIs.

With Alpine Linux 3.15.0, the official bulid system for cloud images in general has changed (i have some docs to write before putting it at https://gitlab.alpinelinux.org/alpine/cloud/alpine-cloud-images -- hopefully will be moved there in a couple days) - this new build system also includes the potential for building customized images, I'll adapt these patches (with suggested fixes), and verify soonish.

[tomalok]

@Cappuccinuo & @JigarDedhia - I've updated the PR to resolve conflicts.

[tomalok]

Obsoleted by #136 (and other merged changes that detect whether or not to use libwrap).