Comment 8 for bug 633681

(continued)
...
add
    set -x
or equiv and figger which script was exiting. But that
will change all the timing and so will cause rpmbuild to "work".

(aside)
Adding
   sleep 2
at beginning of all helper scripts might be a workaround.
Otherwise make sure all child helpers read _ALL_ of stdin
before exiting.

The next level of "fix" is to adjust the timers to fdReadable/fdWritable
or increase the size of the output write buffer in getOutputFrom().

IIRC, shortening the fdWritable timer is part of what is needed so that rpmbuild
can write the entire file list before the helper exits.

THe best fix of all is not write/read from parent <-> child in the same
loop in rpmbuild.