default or selected kernelversion does not have config value CONFIG_BUILD_DOCSRC.
Result is shown for kernelversion 6.5.1

Build targets in Documentation/ tree

configname: CONFIG_BUILD_DOCSRC

Linux Kernel Configuration
└─>Build targets in Documentation/ tree
In linux kernel since version 2.6.27 (release Date: 2008-10-09)  
This option attempts to build objects from the source files in the
kernel Documentation/ tree.

Say N if you are unsure.