CONFIG_ARC64 is not available for thedefaultarchitecture x86.
Result is shown for architecture mips

CONFIG_ARC64 (not configurable)

configname: CONFIG_ARC64

Linux/MIPS Kernel Configuration
└─>Machine selection
└─>ARC64
In linux kernel since version 2.6.12  
depends
CONFIG_SGI_IP27

is depended by
CONFIG_SGI_IP27