CONFIG_DEBUG_SEMIHOSTING is not available for thedefaultarchitecture x86.
Result is shown for architecture arm

Kernel low-level debug output via semihosting I/O


Kernel low-level debugging port
└─>Kernel low-level debug output via semihosting I/O
In linux kernel since version 3.1 (release Date: 2011-10-24)  
Semihosting enables code running on an ARM target to use
the I/O facilities on a host debugger/emulator through a
simple SVC call. The host debugger or emulator must have
semihosting enabled for the special svc call to be trapped
otherwise the kernel will crash.

This is known to work with OpenOCD, as well as
ARM's Fast Models, or any other controlling environment
that implements semihosting.

For more details about semihosting, please see
chapter 8 of DUI0203I_rvct_developer_guide.pdf from ARM Ltd.