CONFIG_BUILTIN_DTB_SOURCE is not available for thedefaultarchitecture x86.
Result is shown for architecture xtensa

DTB to build into the kernel image

configname: CONFIG_BUILTIN_DTB_SOURCE

Linux Kernel Configuration
└─>Platform options
└─>DTB to build into the kernel image
In linux kernel since version 3.10 (release Date: 2013-06-30)  
depends
CONFIG_OF