Simplify logic in configure for listing out files
Simplify logic in configure for listing out files

Add a check that the same header is not both public and internal.

[ci skip]

Rohde-Schwarz-Cybersecurity/botan,webmaster128/botan,webmaster128/botan,webmaster128/botan,randombit/botan,randombit/botan,randombit/botan,Rohde-Schwarz-Cybersecurity/botan,webmaster128/botan,Rohde-Schwarz-Cybersecurity/botan,Rohde-Schwarz-Cybersecurity/botan,randombit/botan,Rohde-Schwarz-Cybersecurity/botan,randombit/botan,Rohde-Schwarz-Cybersecurity/botan,webmaster128/botan