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

CONFIG_EXPORT_UASM (not configurable)

configname: CONFIG_EXPORT_UASM

Linux Kernel Configuration
└─>EXPORT_UASM
In linux kernel since version 2.6.36 (release Date: 2010-10-20)  
is depended by
CONFIG_OCTEON_WDT