with 4.0 rc1:
./configure --with-system-mitkrb5 --without-ad-dc --enable-developer
ERROR: Target 'com_err' in directory /home/bjacke/SVN/master/source4/heimdal_build re-defined as SYSLIB - was SYSLIB
I can't reproduce this. Can you perhaps attach your config.log ?
in master now I also cannot reproduce it, I didn't retry with rc1 now. Let's hope it's fine now. I close this for now, will come back when I see it again :-)