openvpn: remove __DATE__ from options output

reported by:
https://reproducible.debian.net/openwrt/dbd/ar71xx/base/openvpn-nossl_2.3.7-1_ar71xx.ipk.html

Signed-off-by: Dirk Neukirchen <dirkneukirchen@web.de>

SVN-Revision: 46860

package/network/services/openvpn/patches/001-reproducible-remove_DATE.patch

@@ -0,0 +1,10 @@
+--- a/src/openvpn/options.c
++++ b/src/openvpn/options.c
+@@ -102,7 +102,6 @@ const char title_string[] =
+   " [MH]"
+ #endif
+   " [IPv6]"
+-  " built on " __DATE__
+ ;
+ 
+ #ifndef ENABLE_SMALL