When using yum-2.4 from fc4 to build the bootcd, we get a huge

directory under <cdroot>/var/yum/cache (in the 100Mb)
It is thus relocated under usr/relocated/var/cache/ and a symlink is
created, in much the same way as for /var/lib/rpm

Not sure that makes sense to keep all this though, but for now it
allows to proceed