Remove debugging prints from util/add-depends.pl

my $buildfile_new = "$buildfile.$$";

my $depext = $target{dep_extension} || ".d";

my @deps =

    grep { print STDERR "$_ exists: ", -f $_ ? "yes" : "no", "\n"; -f $_ }

    grep { -f $_ }

    map { (my $x = $_) =~ s|\.o$|$depext|; $x; }

    grep { $unified_info{sources}->{$_}->[0] =~ /\.cc?$/ }

    keys %{$unified_info{sources}};

print STDERR "\@deps = ( ", join(", ", @deps), " )\n";

open IBF, $buildfile or die "Trying to read $buildfile: $!\n";

open OBF, '>', $buildfile_new or die "Trying to write $buildfile_new: $!\n";

while (<IBF>) {