Ability to increase partition size

[JamiKettunen]

From https://t.me/ubports_devel/70273 when someone asked about getting a bigger rootfs (assumes linux env and not using the snap):

disk_img=~/.config/UbuntuTouchPdk/data/pdk-image-cache/default/hdd.raw
root_par_start_sector=976563
root_par_offset=$(($root_par_start_sector * 512))

dd if=/dev/zero bs=1G count=15 >> $disk_img
fdisk $disk_img <<EOF
p
d
3
n
p
3
$root_par_start_sector

n
p
w
EOF

loop_dev=$(sudo losetup --offset=$root_par_offset --find --show $disk_img)
sudo e2fsck -fy $loop_dev
sudo resize2fs $loop_dev
sudo losetup --detach $loop_dev

about the "magic numbers" 976563 is the Start sector of the 13.5G ext4 root partition as shown by fdisk -l <path to hdd.raw>, and 500000256 (root_par_offset) is the start sector * sector size (512 bytes), so the partition start offset in bytes

Not sure if this is super useful since not many (if any) people have needed it so far, but gonna leave this here just in case it might be.

[JamiKettunen]

Closing as #45 already existed.