Makefile: Remove mkinitcpio-archiso specific targets

Makefile:
Remove all code specific to mkinitcpio-archiso.
Allow overriding PREFIX (defaults to /usr/local).
Gather scripts to check more generically.
Add abstractions for installation directories.
7 jobs for issues/47 in 13 seconds (queued for 7 seconds)
Status Name Job ID Coverage
  Check
failed check #30405

00:00:13

 
  Build
skipped build_long: [baseline iso] #30408
fast-single-thread
skipped build_long: [baseline netboot] #30409
fast-single-thread
skipped build_long: [releng iso] #30410
fast-single-thread
skipped build_long: [releng netboot] #30411
fast-single-thread
skipped build_short: [baseline bootstrap] #30406
skipped build_short: [releng bootstrap] #30407
 
Name Stage Failure
failed
check Check
(1/4) Reloading system manager configuration...
Skipped: Current root is not booted.
(2/4) Arming ConditionNeedsUpdate...
(3/4) Warn about old perl modules
(4/4) Registering Haskell modules...
$ make lint
make: *** No rule to make target 'lint'. Stop.
Cleaning up file based variables
ERROR: Job failed: exit code 1