Revert "config: build with selinux for all variants but codefirex"

This reverts commit 20a4b9b9aa3a75384f47ca768155b45f24560b57.

Conflicts:
	core/config.mk
Revert "Revert "Establish explicit dependency on selinux file_contexts.""

This reverts commit bd0b9a4b7cea6dbb6c0b12f6d274afa2d5f9aec5.