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

CONFIG_SYS_SUPPORTS_BIG_ENDIAN (not configurable)

configname: CONFIG_SYS_SUPPORTS_BIG_ENDIAN

Linux/MIPS Kernel Configuration
└─>SYS_SUPPORTS_BIG_ENDIAN
In linux kernel since version 2.6.15 (release Date: 2006-01-02)