CONFIG_ARC_CANT_LLSC is not available for thedefaultarchitecture x86.
Result is shown for architecture arc

CONFIG_ARC_CANT_LLSC (not configurable)

configname: CONFIG_ARC_CANT_LLSC

Linux Kernel Configuration
└─>ARC Architecture Configuration
└─>ARC CPU Configuration
└─>ARC_CANT_LLSC
In linux kernel since version 3.1 (release Date: 2011-10-24)  
is depended by
CONFIG_ARC_CPU_750D