After seeing a bunch of silent build failures, like this:

>   GEN      criu/pie/parasite-native-blob.h
> criu/pie/Makefile:121: recipe for target 'criu/pie/parasite-native-blob.h' failed

I finally took a look at why are they silent, only to discover that
compel prints errors to stdout, and of course its stdout is silenced
in criu/pie/Makefile (unless you run make with V=1, in which case
it prints tons and tons of very useful information). I am so shocked
by this evil plan!

Anyway, let's print errors to stderr like all sane programs do.
Signed-off-by: Kir Kolyshkin <kir@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>