exim: enable plaintext and cram-md5 authenticators

Fixes #8126

Signed-off-by: Mirko Langisch <pud@nerdpunx.net>
Acked-by: Bernd Kuhls <bernd.kuhls@t-online.de>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/exim/exim.mk

@@ -46,6 +46,8 @@ define EXIM_USE_DEFAULT_CONFIG_FILE
 	$(call exim-config-change,PCRE_CONFIG,no)
 	$(call exim-config-change,HAVE_ICONV,no)
 	$(call exim-config-unset,EXIM_MONITOR)
+	$(call exim-config-change,AUTH_PLAINTEXT,yes)
+	$(call exim-config-change,AUTH_CRAM_MD5,yes)
 endef
 
 ifeq ($(BR2_PACKAGE_DOVECOT),y)