Support configurable PREFIX

[michaelforney]

This will allow users to install oasis alongside their existing operating system by setting config.prefix=os.getenv('HOME')..'/oasis'.

[Intensity]

@michaelforney : I'm wondering if this functionality is known to work at this time. I see an entry for "prefix" in the config.lua file but it seems to be framed as an "install" prefix, rather than a base prefix from which the packages look for any related dependencies and files.

Is there a means to rebuild the system in a way that all binaries, configuration files, and any other package specific data is fully hosted under a user-defined path? In that case I'd imagine that the packages built would need to know to add this prefix in front of the usual paths they're used to using, so that Oasis prefixed can fully co-exist alongside another distribution. For example, instead of a package referencing /etc/somewhere, it would have to reference /opt/oasis/etc/somewhere (if /opt/oasis is the user's choice for prefix).

Perhaps it's available but I'm not aware of a step-by-step guide. I've been following the (re)build process given in the README that's packaged with the latest qemu image file, but since I less understand the build tool I'm not sure if there's a separate "make install" counterpart command involving git or samu.