Upgrade BlackArch to 2017.12.11

src/blackarch.ipxe

@@ -9,6 +9,7 @@ goto ${menu}
 set os BlackArch Linux
 menu ${os} Installers
 item --gap Official Releases
+item 2017.12.11 ${space} ${os} 2017.12.11
 item 2017.08.30 ${space} ${os} 2017.08.30
 choose blackarch_version || goto blackarch_exit
 goto blackarch_boot