CONFIG_TILEGX is not available for thedefaultarchitecture x86.
Result is shown for architecture tile

Building with TILE-Gx (64-bit) compiler and toolchain

modulename: futex_64.ko

configname: CONFIG_TILEGX

Linux/TILE Kernel Configuration
└─>Building with TILE-Gx (64-bit) compiler and toolchain
In linux kernel since version 2.6.36 (release Date: 2010-10-20)  
source code:
arch/tile/kernel/

depends
CONFIG_EXPERIMENTAL