dpkg-gencontrol: Move grep inside an if block

This makes the test explicit, and avoids confusing perlcritic of this
being a void grep.

Fixes BuiltinFunctions::ProhibitVoidGrep.

scripts/dpkg-gencontrol.pl

@@ -209,10 +209,11 @@ foreach (keys %{$pkg}) {
 			     scalar(@invalid_archs)),
 		    join("' `", @invalid_archs))
 		if @invalid_archs >= 1;
-	    grep(debarch_is($host_arch, $_), @archlist) ||
+	    if (! grep(debarch_is($host_arch, $_), @archlist)) {
 		error(_g("current host architecture '%s' does not " .
 			 "appear in package's architecture list (%s)"),
 		      $host_arch, "@archlist");
+	    }
 	    $fields->{$_} = $host_arch;
 	}
     } else {

test/100_critic.t

@@ -40,6 +40,7 @@ my @policies = qw(
     BuiltinFunctions::ProhibitStringySplit
     BuiltinFunctions::ProhibitUniversalCan
     BuiltinFunctions::ProhibitUniversalIsa
+    BuiltinFunctions::ProhibitVoidGrep
     BuiltinFunctions::RequireGlobFunction
     BuiltinFunctions::RequireSimpleSortBlock
     ClassHierarchies::ProhibitAutoloading