Newer versions of gpgme.h require _FILE_OFFSET_BITS defined
to the same value which gpgme-devel was compiled with.
I assume here we all use _FILE_OFFSET_BITS=64.
The gpgmefw.h patch is required because exception.cpp for some
reason does not include config-gpgme++.h, but <gpgme.h>

--- gpgme++/config-gpgme++.h.cmake	2014-11-04 22:19:27.000000000 +0100
+++ gpgme++/config-gpgme++.h.cmake	2015-07-28 15:34:47.449866029 +0200
@@ -134,4 +134,9 @@
 #define     GPG_ERR_SOURCE_DEFAULT ((gpg_err_source_t)22)
 #endif
 
+#ifndef _FILE_OFFSET_BITS
+/* required to build against recent gpgme.h */
+#define _FILE_OFFSET_BITS 64
+#endif
+
 #endif /* __GPGMEPP_CONFIG_GPGMEPP_H__ */
--- gpgme++/gpgmefw.h	2014-11-04 22:19:27.000000000 +0100
+++ gpgme++/gpgmefw.h	2015-07-28 15:39:40.636865160 +0200
@@ -23,6 +23,10 @@
 #ifndef __GPGMEPP_GPGMEFW_H__
 #define __GPGMEPP_GPGMEFW_H__
 
+#ifndef _FILE_OFFSET_BITS
+#define _FILE_OFFSET_BITS 64
+#endif
+
 struct gpgme_context;
 typedef gpgme_context * gpgme_ctx_t;