CONFIG_MAC is not available for thedefaultarchitecture x86.
Result is shown for architecture m68k

Macintosh support

configname: CONFIG_MAC

Linux Kernel Configuration
└─>Macintosh support
In linux kernel since version 2.6.12  
This option enables support for the Apple Macintosh series of
computers (yes, there is experimental support now, at least for part
of the series).

Say N unless you're willing to code the remaining necessary support.