release: Comply with Azure Marketplace requirements for aarch64

[lwhsu]

Summary

This is based on D52734, ensure the BOOTPARTSOFFSET parameter only appended to
the first boot partition.

amd64:

=>      34  62984125  md0  GPT  (30G)
        34      2014       - free -  (1.0M)
      2048       122    1  freebsd-boot  (61K)
      2170     66584    2  efi  (33M)
     68754  62914560    3  freebsd-ufs  (30G)
  62983314       845       - free -  (423K)

aarch64:

=>      34  62984125  md0  GPT  (30G)
        34      2014       - free -  (1.0M)
      2048     66584    1  efi  (33M)
     68632  62914560    2  freebsd-ufs  (30G)
  62983192       967       - free -  (484K)

Purposed commit message:

release: Comply with Azure Marketplace requirements for aarch64

Azure requires the first 1 MB (2,048 sectors) of the OS disk to remain
empty for VM images:

  https://learn.microsoft.com/partner-center/marketplace-offers/azure-vm-certification-faq#vm-images-must-have-1-mb-of-free-space

Also append the BOOTPARTSOFFSET suffix for aarch64 images, which only
has an ESP partition for booting.

Co-authored-by:	Brad Davis <[e-mail]>
Sponsored by:	The FreeBSD Foundation

[cperciva]

Where is BOOTPARTSOFFSET defined? Is there a missing patch to release/tools/azure.conf ?

[lwhsu]

In D53628#1224327, @cperciva wrote:

Where is BOOTPARTSOFFSET defined? Is there a missing patch to release/tools/azure.conf ?

In release/tools/azure.conf it's VM_BOOTPARTSOFFSET

In this file's vm_create_disk() it is converted to BOOTPARTSOFFSET and used in

	case "${TARGET}:${TARGET_ARCH}" in
		amd64:amd64 | i386:i386)

And this patch doing the same when dealing with ESP.

[cperciva]

Ah never mind, I accidentally grepped for "BOOTPARTOFFSET" instead of "BOOTPARTSOFFSET".