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

CONFIG_SYS_SUPPORTS_MICROMIPS (not configurable)

modulename: uasm-micromips.ko

configname: CONFIG_SYS_SUPPORTS_MICROMIPS

Linux Kernel Configuration
└─>Kernel type
└─>SYS_SUPPORTS_MICROMIPS
In linux kernel since version 3.1 (release Date: 2011-10-24)  
source code:
arch/mips/mm/uasm-micromips.c