official-images cleanup and improvements

[yosifkit]

• moved to be FROM buildpack-deps:jessie-scm, this gives users access to tools like git and curl, without adding in all the extra c-libs that regular buildpack-deps has.
  • are C library dependencies in perl6 modules very common? if so, we should switch this to just use buildpack-deps and consider adding a :slim version.
• install deps that are needed for build and remove them in the same layer to slim the image
• remove the source (if the source dir is useful in the image I can pull it out of the rm)
• swap some ordering for better docker caching of layers

[hoelzro]

@yosifkit thanks for the pr! regarding c library dependencies, are you asking if perl 6 modules need to compile c libraries, or if they reference libraries under /usr/lib?

[tianon]

I think a good example would be XML::LibXML for Perl 5, which is a wrapper around libxml2. Is this as common in Perl 6 as it is in 5, or is it more like the Go world, where the majority of libraries get re-implemented natively?

[hoelzro]

Thanks for the cleanup @yosifkit, and for the input @tianon!

[hoelzro]

Ok, I just tried all of the Star modules, and they all look good on the generated image!