trn: Add NOT_FOR_BULK_PLATFORM for Darwin.

For some reason this software tries to locate libc.  On at least modern
versions of macOS this fails and so it runs an interactive program to
ask the user where it lives.  This causes infinite loops in bulk builds.

news/trn/Makefile

@@ -1,4 +1,4 @@
-# $NetBSD: Makefile,v 1.52 2022/12/15 11:30:36 jperkin Exp $
+# $NetBSD: Makefile,v 1.53 2024/04/24 14:39:31 jperkin Exp $
 
 DISTNAME=		trn-4.0-test77
 PKGNAME=		trn-4.77
@@ -13,6 +13,9 @@ LICENSE=		trn-license
 
 PKG_SYSCONFSUBDIR=	nntp
 
+# Runs an interactive program to determine where libc is.
+NOT_FOR_BULK_PLATFORM+=	Darwin-*-*
+
 .include "options.mk"
 
 # TRN_HOSTBITS determines the number of "name segments" (x.y.z.com), counting