kconfig: Terminate menu blocks with a comment in the generated config

Currently menu blocks start with a pretty header but end with nothing in
the generated config. So next config options stick together with the
options from the menu block.

Let's terminate menu blocks in the generated config with a comment and
a newline if needed. Example:

...
CONFIG_BPF_STREAM_PARSER=y
CONFIG_NET_FLOW_LIMIT=y

#
# Network testing
#
CONFIG_NET_PKTGEN=y
CONFIG_NET_DROP_MONITOR=y
# end of Network testing
# end of Networking options

CONFIG_HAMRADIO=y
...
Signed-off-by: Alexander Popov <alex.popov@linux.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

scripts/kconfig/confdata.c

@@ -867,6 +867,7 @@ int conf_write(const char *name)
 	const char *str;
 	char tmpname[PATH_MAX + 1], oldname[PATH_MAX + 1];
 	char *env;
+	bool need_newline = false;
 
 	if (!name)
 		name = conf_get_configname();
@@ -912,12 +913,16 @@ int conf_write(const char *name)
 				     "#\n"
 				     "# %s\n"
 				     "#\n", str);
+			need_newline = false;
 		} else if (!(sym->flags & SYMBOL_CHOICE)) {
 			sym_calc_value(sym);
 			if (!(sym->flags & SYMBOL_WRITE))
 				goto next;
+			if (need_newline) {
+				fprintf(out, "\n");
+				need_newline = false;
+			}
 			sym->flags &= ~SYMBOL_WRITE;
-
 			conf_write_symbol(out, sym, &kconfig_printer_cb, NULL);
 		}
 
@@ -929,6 +934,12 @@ int conf_write(const char *name)
 		if (menu->next)
 			menu = menu->next;
 		else while ((menu = menu->parent)) {
+			if (!menu->sym && menu_is_visible(menu) &&
+			    menu != &rootmenu) {
+				str = menu_get_prompt(menu);
+				fprintf(out, "# end of %s\n", str);
+				need_newline = true;
+			}
 			if (menu->next) {
 				menu = menu->next;
 				break;