bigfin.spec: rm BuildRoot
bigfin.spec: rm BuildRoot

This has not been needed since RHEL 5.

Change-Id: If942eb3a01f1596c8403e4d13854fec647df58dc
Signed-off-by: Ken Dreyer <940dddfbf8b0685439b7ecf27daa0ba58b359a2c@redhat.com>

skyrings/bigfin,skyrings/bigfin,skyrings/bigfin