Red Hat :: Why Rpmbuild Deletes The BUILD Directory

I'm using rpmbuild 4.8.0 to build my rpm package on RHEL6. The spec file works just fine with any other Linux Releases, including RHEL5. But at the end, build failed with:
"shell-init error retrieving current directory: getcwd: cannot access parent directories: No such file or directory" I found that rpmbuild tried to compare the BUILD directory with the root filesystem, it will delete the BUILD directory if it's not '/'. My working directory is /tmp/test, so something like this in the /var/tmp/rpm-tmp file:

Code:

cd "/tmp/test/BUILD"
[ "RPM_BUILD_ROOT" != "/" ] && rm -rf "${RPM_BUILD_ROOT}"

I think this is the reason why the command failed. And I can't find the two lines of similar code in an earlier version of rpmbuild on RHEL5.