Try it and see? I can't find any concrete documentation one way or the
other, although it seems BuildRequires generally follows what Requires
does.  You may need to ask the people who maintain RPM.

There are other issues in the spec file, however, like:

        --with-libfreeradius-ldap-include-dir=/usr/local/openldap/include \
        --with-libfreeradius-ldap-lib-dir=/usr/local/openldap/lib64 \

are specific to LTB, might want to do something like they did around line
447 to only do this if the LTB openldap is in use.