Adds:
1. grub-efi package mappings
2. efi-64 support
3. default (openrc) arm64 profile
4. systemd arm64 profile
Cleans up the keywords and use flags in 02-gentoo-02-flags. Most stuff
was stablized. Also cleaned up some formatting for the if statements.
Enables less trusted overlays (up to the end user to verify).
in 10-gentoo-image I cleaned up some bash lint things as well.
using && instead of -a and avoiding $?
Change-Id: I3dffe1aab4bbdc4946a9bf2269bf0cde49529a4e
bea81bd234