When running buildinstall on customized distribution it should be run from /usr/lib/anaconda-runtime directory or buildinstall is unable to call itself (second run). There should be path to buildinstall directory when calling itself. I did not tryed Rawhide version yet.
Fedora Core 1 has the same problem (anaconda-9.2-2).
It should be copying from /usr/lib/anaconda-runtime into buildinstall.tree.$$ -- is that not happening?
Closing due to lack of information. Please reopen if you have more data to provide.