Build aarch64-alpine-linux-musl for Alpine Linux on arm64

[ronaldtse]

Similar to metanorma/emf2svg-ruby#17

[ronaldtse]

• Rubygems now supports differentiation of platform between glibc and musl: Support non gnu libc linux platforms rubygems/rubygems#5852 , which works from 3.1.0.pre.1 onwards
• We wait for the merging of Backport non gnu libc linux support from RubyGems rubygems/rubygems#4488 for bundler to work
• Then we can re-do this task of publishing the gem on the musl platforms

[maxirmx]

@ronaldtse
I have some doubts that libarchieve (and this gem) are required at all
Excavate uses libarchive to work with pkg files (xar archives) but this format is supported by 7zip. I believe we can uses seven-zip gem.

[ronaldtse]

@maxirmx that is a great discovery -- let's try using the seven-zip gem to support excavate. If that is complete, we can drop maintenance for this gem.

[maxirmx]

@ronaldtse
(Writing it here because https://github.com/fontist/seven_zip_ruby has issues disabled)

The latest version of core p7zip library (16) can handle pkg (XAR) files but seven_zip_ruby gem now uses very old version - as of 2009 that does not support XAR.

I believe we can upgrade p7zip but does not look like an easy move. It may take several weeks. I am not sure if it is feasible. Please advise.