Allow Public-Domain as a valid license
Public-Domain is not a valid SPDX license identifier and causes
abuild sanitycheck warnings. The Alpine project does consider public domain a valid license and uses it in 34 different packages. This change adds the
Public-Domain license as an override for
sanitycheck to avoid warnings for these packages.
See: aports!8863 (merged)
Related: aports!8899 (merged)