CONFIG_BUILTIN_DTB_NAME is not available for the selected architecture x86.
Result is shown for architecture mips

Source file for built-in DTB

configname: CONFIG_BUILTIN_DTB_NAME

Linux Kernel Configuration
└─>Source file for built-in DTB
In linux kernel since version 4.19.310 (release Date: 2024-03-15)
Base name (without suffix, relative to arch/mips/boot/dts/loongson)
for the DTS file that will be used to produce the DTB linked into
the kernel.