dovecot 2.4.0: Unable to build without LDAP/LUA headers/libs.

I'm getting LDAP/LUA build errors with dovecot 2.4.0 even when --without-lua and --without-ldap is specified: eg.

In file included from db-ldap-settings.c:9: ../../src/lib-ldap/ldap-settings-parse.h:4:10: fatal error: ldap.h: No such file or directory 4 | #include <ldap.h> | ^~~~~~~~ compilation terminated. make[3]: *** [Makefile:2134: auth-db-ldap-settings.o] Error 1