Avoid sendmail build dependency
    
    sudo should be compatible with any MTA, any of which in Fedora provide
    /usr/sbin/sendmail, and is used at build time only to determine its
    location.  Instead of generalizing the build requirement (e.g. for RHEL
    10 which includes only postfix), we can just tell sudo its location
    during configure, in which case it is not needed at all to build.
    
    However, doing so uncovered that systemd's presence was being relied
    upon without being specified.  This too can be avoided by using the
    macros to define the proper tmpfiles location during configure.