I'm having a tough time building mod_auth_cas on httpd:2.4.23-alpine (Alpine Linux), as opposed to httpd:2.4.23 (Debian). mod_auth_cas.c imports <error.h>, which isn't provided by musl/libc-dev on Alpine.

Is error.h strictly needed? I scanned through mod_auth_cas.c, but couldn't find an obvious use of it.