CONFIG_MAC is not available for the default architecture x86.
Result is shown for architecture m68k

Macintosh support

configname: CONFIG_MAC

Linux/68k Kernel Configuration
└─> Platform dependent setup
└─> Macintosh support

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.