CONFIG_TASK_SIZE_BOOL is not available for the selected architecture x86.
Result is shown for architecture microblaze

Set custom user task size

configname: CONFIG_TASK_SIZE_BOOL

Linux Kernel Configuration
└─>Kernel features
└─>Set custom user task size
In linux kernel since version 2.6.15 (release Date: 2006-01-02)
This option allows you to set the amount of virtual address space
allocated to user tasks. This can be useful in optimizing the
virtual memory layout of the system.

Say N here unless you know what you are doing.