CONFIG_ARCH_ALPINE is not available for thedefaultarchitecture x86.
Result is shown for architecture arm64

Annapurna Labs Alpine platform

configname: CONFIG_ARCH_ALPINE

Linux Kernel Configuration
└─>Platform selection
└─>Annapurna Labs Alpine platform
In linux kernel since version 3.10 (release Date: 2013-06-30)  
This enables support for the Annapurna Labs Alpine
Soc family.