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

Macintosh support

modulename: head.ko

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. If you plan to use this kernel on a Mac, say Y here and
browse the documentation available at <http://www.mac.linux-m68k.org/>;
otherwise say N.

source code:
arch/m68k/kernel/