prevent doubly passing our CFLAGS
--- libesmtp-1.0.6.orig/plain/Makefile.am	2010-08-08 17:45:54.000000000 +0200
+++ libesmtp-1.0.6/plain/Makefile.am	2014-06-05 22:29:56.668682572 +0200
@@ -3,7 +3,7 @@
 libdir = @plugindir@
 
 INCLUDES = -I@srcdir@
-AM_CFLAGS = @CFLAGS@ @EXTRA_CFLAGS@
+AM_CFLAGS = @EXTRA_CFLAGS@
 
 lib_LTLIBRARIES = sasl-plain.la