CONFIG_ARC_UBOOT_SUPPORT is not available for thedefaultarchitecture x86.
Result is shown for architecture arc
default or selected kernelversion does not have config value CONFIG_ARC_UBOOT_SUPPORT.
Result is shown for kernelversion 6.7-rc3

Support uboot arg Handling


Linux Kernel Configuration
└─>ARC Architecture Configuration
└─>Support uboot arg Handling
In linux kernel since version 4.1 (release Date: 2015-06-21)  
ARC Linux by default checks for uboot provided args as pointers to
external cmdline or DTB. This however breaks in absence of uboot,
when booting from Metaware debugger directly, as the registers are
not zeroed out on reset by mdb and/or ARCv2 based cores. The bogus
registers look like uboot args to kernel which then chokes.
So only enable the uboot arg checking/processing if users are sure
of uboot being in play.