Description of problem: BuildRoot value is hardcoded in spec to /var/tmp/gcc-root. It should be something like %{_tmppath}/%{name}-%{version}-root.
It really doesn't matter, it is overridden almost always anyway. There are many packages that have similar buildroot values. All that matters is whether the BuildRoot tag is present or not.
There probably is some other issue in gcc spec file. GCC was the only package out of all RHELv4 updates which completely ignored %_tmppath %(eval 'echo $HOME/tmp') in ~/.rpmmacros and continued to place its files in /var/tmp/gcc-root
Original submitter is not able to reopen the but so I am creating another one.