scripts: time.pl: Don't print the time on stderr

scripts: time.pl: Don't print the time on stderr

Having the build time written on stderr make it appear with V=w
although it is not an error or warning. Just write the time on stdout
to have it part of the build log like all the rest, but not clutter
the output when only warnings and errors should be shown.

Signed-off-by: Alban Bedel <[email protected]>