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.

 --- gcc-4.1.2.orig/gcc/configure.ac	2006-11-13 23:09:55.000000000 +0100

 +++ gcc-4.1.2/gcc/configure.ac	2007-03-04 23:34:53.000000000 +0100

 @@ -2435,7 +2435,7 @@

  	tls_first_minor=14

  	tls_as_opt="-m64 -Aesame --fatal-warnings"

  	;;

 -  sh-*-* | sh[34]-*-*)

 +  sh-*-* | sh[34]*-*-*)

      conftest_s='

  	.section ".tdata","awT",@progbits

  foo:	.long	25

 --- gcc-4.1.2.orig/gcc/configure	2006-11-13 23:09:55.000000000 +0100

 +++ gcc-4.1.2/gcc/configure	2007-03-04 23:34:53.000000000 +0100

 @@ -14762,7 +14762,7 @@

  	tls_first_minor=14

  	tls_as_opt="-m64 -Aesame --fatal-warnings"

  	;;

 -  sh-*-* | sh[34]-*-*)

 +  sh-*-* | sh[34]*-*-*)

      conftest_s='

  	.section ".tdata","awT",@progbits

  foo:	.long	25