Build improvements (and fixes) to facilitate downstream packaging

[attipaci]

• Changes to build to make packaging easier #23 -- Various build improvements with easier packaging in mind
• SUPERNOVAS_VERSION_STRING ill defined in novas.h #24 -- Fix ill-defined SUPERNOVAS_VERSION_STRING
• Fixes to cio_file (normally used only at build time).

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 98.79%. Comparing base (5afc6af) to head (817fddc).
Report is 4 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #25   +/-   ##
=======================================
  Coverage   98.79%   98.79%           
=======================================
  Files           3        3           
  Lines        1987     1987           
  Branches      370      370           
=======================================
  Hits         1963     1963           
  Misses          7        7           
  Partials       17       17           

Flag	Coverage Δ
unittests	98.79% <ø> (ø)

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