Update of the bootcodes after zpool uprade zroot pool

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During the Victoria Day long weekend, I took the time to
upgrade my two FreeBSD computers from FreeBSD 13.2 to 14.0.
The process went well as I always do a review of the upgrade
chapter in MWL's book Absolute FreeBSD.

At the end of the upgrade process I ran a typical
% zpool status and
# zpool scrub 

Zpool status prompts to zpool upgrade to gain access to new
features and thinking that my system now runs on the latest 
RELEASE I went on and
# zpool upgrade zroot...
Things were fine after that and at the end of the day I 
shutted down the system.
To my surprise, next time I tried to turn the computer on,
the system wasn't able to boot.
It prompted the messages below,
  
Consoles: EFI console
ZFS: unsupported feature: com.delphix:head_errlog
ZFS: pool zroot is not supported
     Reading loader env vars from /efi/freebsd/loader.env
Setting currdev to disk0p1:
FreeBSD/amd64 EFI loader. Revision 1.1

Reading at the FreeBSD forums, lead to me understand that it
must be related to skipping updating the bootcode after
upgrading the zroot pool.
Last time I upgraded a zfs pool it was when ZFS 2.0 came out.

I created a bootable USB thumb drive with NomadBSD.
The NomadBSD project saved me in the past a few more times.
I managed to zpool import my zroot pool and copy my home directory.

After having my data in a safe place I felt more confident
to try updating the bootcode. 

Check if the partition scheme is GPT.
% gpart show nda0

Mount the efi boot partition to /mnt in order to update the 
bootcode.
# mount -t msdosfs /dev/nda0p1 /mnt

Copy the updated bootcode to the boot location
NomadBSD and my system both run 14.0-RELEASE. 
# cp /boot/loader.efi /mnt/efi/boot/bootx64.efi

Remove the mounted partition
# umount /mnt

... and reboot...
With fingers crossed, I waited to see the Beastie menu showing up.
My system booted properly!

Special thanks to Emrion, who wrote the instructions on updating
the bootcode for GPT scheme in the FreeBSD forum.
https://forums.freebsd.org/threads/update-of-the-bootcodes-for-a-gpt-scheme-x64-architecture.80
163/
I also want to thank the GTABUG community who kindly received
my email while I was in panic mode.