Makefile: Adapt to new project layout

Makefile:
Adapt the file to the new project layout and contents.
Remove any archiso specific calls.
Allow overriding installation prefix using `PREFIX` (defaults to `/usr/local`).
Rename lint target to shellcheck.
Add a shfmt target to call shfmt in (it is not yet added to the check target).
Install files verbosely and more generically.

0 files changed, 0 insertions, 0 deletions