ls: /var/www/html/atmail: No such file or directory
Did you put atmail=no in /usr/local/directadmin/custombuild/options.txt
You can ignore that error (CustomBuild checks for that directory whether it exists or not), it will be fixed soon.
cd /usr/local/directadmin
wget -O custombuild.tar.gz http://www.custombuild.eu/custombuild-1.1.15.tar.gz
tar xzf custombuild.tar.gz
cd /usr/local/directadmin
wget -O custombuild.tar.gz http://www.custombuild.eu/custombuild-1.2.9.tar.gz
tar xzf custombuild.tar.gz