Resize of root disk doesn't work on Alpine 3.12.1 aarch64

Created by: tsarna

I created a VM using the new aarch64 AMIs for Alpine 3.12.1 with a 4GB root disk, and just noticed that the root filesystem is only ~1G.

I think the issue is the different partitioning on ARM. On amd64, the root disk is just /dev/nvme0n1, but on ARM I see:

/dev/nvme0n1p2          985.0M    167.0M    751.1M  18% /
/dev/nvme0n1p1            5.0M    278.0K      4.7M   5% /boot/efi

I think resize2fs isn't able to expand the filesystem since it's already occupying the whole partition, and when I duplicate the resize command that the bootstrap runs:

$ resize2fs /dev/nvme0n1p2
resize2fs 1.45.6 (20-Mar-2020)
The filesystem is already 260347 (4k) blocks long.  Nothing to do!

So I think the resize step needs to check if the root fs is a partition or raw disk, and if a partition needs to repartition.