CONFIG_AMIGA is not available for thedefaultarchitecture x86.
Result is shown for architecture m68k
Amiga support
configname: CONFIG_AMIGA
Linux Kernel Configuration
└─>Amiga support
In linux kernel since version 2.6.12
This option enables support for the Amiga series of computers. If
you plan to use this kernel on an Amiga, say Y here and browse the
material available in Documentation/m68k; otherwise say N.
you plan to use this kernel on an Amiga, say Y here and browse the
material available in Documentation/m68k; otherwise say N.