source builder issue (unstable: expat-2.1.0-1 missing)

[Karel Gardas]

Hello,

while trying source builder on CentOS 6.x on AMD64 machine I've hit 
following issue:

../source-builder/sb-set-builder --log=sparc.log 
--prefix=/home/karel/sfw/rtems-sparc-head unstable/4.11/rtems-sparc.bset
RTEMS Source Builder - Set Builder, v0.2.0
Build Set: unstable/4.11/rtems-sparc.bset
error: unstable/4.11/rtems-sparc.bset:17: cannot find file: expat-2.1.0-1
Build FAILED

this is using today's source buidler head attempting to build RTEMS 
unstable/4.11 tools.

Is there anything I may done in order to fix that?

Thanks!
Karel