Bug in local_exec

[Daniel Jacobowitz]

We discovered today that using remote_exec with just an output file
doesn't work.  Put this in a .exp file and run it with runtest:

remote_exec host "sh -c {gcc -v 2>&1}" "" "" "outfile"

You'll get a TCL exception.  After a while debugging it, we worked out
that this is because local_exec uses:
   open "| sh ..." w
The problem with that is we then open that as a spawn, and read from
it, waiting for EOF.  But you can't read from the write end of a pipe.
The read returns EBADF and expect throws in the towel.

This works fine:
remote_exec host "sh -c {gcc -v 2>&1}" "" "/dev/null" "outfile"

I think using mode w here is invalid.

-- 
Daniel Jacobowitz
CodeSourcery