CONFIG_SYS_SUPPORTS_MIPS16 is not available for thedefaultarchitecture x86.
Result is shown for architecture mips

CONFIG_SYS_SUPPORTS_MIPS16 (not configurable)

configname: CONFIG_SYS_SUPPORTS_MIPS16

Linux Kernel Configuration
└─>Kernel type
└─>SYS_SUPPORTS_MIPS16
In linux kernel since version 3.16 (release Date: 2014-08-03)  
This option must be set if a kernel might be executed on a MIPS16-
enabled CPU even if MIPS16 is not actually being used. In other
words, it makes the kernel MIPS16-tolerant.