[...]

g: Could not canonicalize hostname: giant
Building target platforms: i686-linux
Wrote: /home/users/builder/rpm/SRPMS/postfix-3.6.4-1.src.rpm
exit status 0
Tagging with prefix: tld/
Already on 'master'
No conditional flags passed
from available:
--with   :	
--without:	 cdb epoll ldap mysql pgsql sasl sqlite ssl
Writing git revision for tag tld/postfix-3.6.4-1
error: Macro %_builddir has empty body
error: Macro %_builddir has empty body
Executing(--clean): env -i TMP=/home/users/builder/tmp HOME=/home/users/builder PATH=/bin:/usr/bin:/usr/sbin:/sbin:/usr/X11R6/bin TMPDIR=/home/users/builder/tmp  /bin/sh -e /home/users/builder/tmp/rpm-tmp.25792
+ umask 022
+ cd /home/users/builder/rpm/BUILD
+ rm -rf postfix-3.6.4
Begin-TLD-Builder-Info
Build-Time: user:2.12s sys:1.37s real:3.14s (faults io:0 non-io:218016)
Files queued for ftp:
   4774351 postfix-3.6.4-1.src.rpm
       185 postfix-3.6.4-1.src.rpm.uploadinfo
End-TLD-Builder-Info