Ah! I finally have a progress bar that doesn't stall the build!
- pipe size in Linux is only 8*512=4096 bytes
- pipe size is not setable
- when the feeding process spits out data faster than the eating
process can read it, then the feeding process stalls after 4KiB
of data sent to the pipe
- for us, the progress bar would spawn a sub-shell every line,
and the sub-shell would in turn spawn a 'date' command.
Which was sloooww as hell, and would cause some kind of a
starvation: the pipe was full most of the time, and the
feeding process was stalled all this time.

Now, we use internal variables and a little hack based onan offset
to determine the elapsed time. Much faster this way, but still
CPU-intensive.

 Status: committed upstream after 6.3.  Fixes some terminal mangling in

 gdbtui.

 2004-12-04  Daniel Jacobowitz  <dan@debian.org>

 	PR tui/1703

 	* linux-nat.c (linux_tracefork_child): Use _exit instead of exit.

 	Suggested by Joshua Neuheisel.

 Index: gdb-6.3/gdb/linux-nat.c

 ===================================================================

 --- gdb-6.3.orig/gdb/linux-nat.c	2004-12-08 18:22:04.996973094 -0500

 +++ gdb-6.3/gdb/linux-nat.c	2004-12-08 18:22:20.386956067 -0500

 @@ -147,7 +147,7 @@ linux_tracefork_child (void)

    ptrace (PTRACE_TRACEME, 0, 0, 0);

    kill (getpid (), SIGSTOP);

    fork ();

 -  exit (0);

 +  _exit (0);

  }

  /* Wrapper function for waitpid which handles EINTR.  */