VMS: Fix run of generic generator programs in descrip.mms.tmpl

For a generic program, always go through the MCR utility.
Reviewed-by: NPaul Dale <pauli@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/15397)

Configurations/descrip.mms.tmpl

@@ -984,7 +984,7 @@ EOF
           $gen0 = platform->bin($gen0);
           return <<"EOF";
 $args{src} : $gen0 $deps
-	PIPE $gen0$gen_args > \$@
+	PIPE MCR $gen0$gen_args > \$@
 EOF
       } else {
           #