[Feature Request] Try to support Graviton-based Instance-Types

[ferricoxide]

Is your feature request related to a problem? Please describe.

AMIgen8 is currently only known to support x86_64 instance-types. Some users will want to be able to use Graviton-based instance-types, particularly the ML-optimized ones: makes sense to try to ensure that AMIgen8 can also produce Graviton-compatible instance-types.

Describe the solution you'd like

Verify whether current automation can be used to produce Graviton (ARM) compatible instances types. Update code as necessary if not.

Use $ aws ec2 describe-images --owner 309956199498 --filters 'Name=name,Values=RHEL-8*' --query 'Images[?Arch]' to identify candidate bootstrap AMIs

Describe alternatives you've considered

N/A

Additional context

AWS is increasing efforts around their ARM-oriented Graviton instance types, particularly for functionality like AI and ML.

[ferricoxide]

Looks like Graviton AMIs need to use EFI boot-disks. At bare-minimum, need to add the shim-aa64, grub2-efi-aa64 and grub2-efi-aa64-modules RPM to the project-README's In addition to the RPM-group's contents dependency-list and to the aarch64 invocation of the OSpackages.sh script's -e list.

[ferricoxide]

Looks like need to make the /sbin/grub2-install step (PostBuild.sh script's line 369) conditional on either platform or explicit-selection of UEFI bootloader. When using /sbin/grub2-install on UEFI platforms (like aarch64), the PostBuild.sh script will fail with:

grub2-install: error: this utility cannot be used for EFI platforms because it does not support UEFI Secure Boot.

Error-message.