New review comment by tornaria on void-packages repository

https://github.com/void-linux/void-packages/pull/29780#discussion_r703902693

Comment:
If not fixing the issue I described above, I would say at least leave the `efibootmgr -qo $bootorder` in place. Without it, the last kernel installed will take priority which is not very convenient (e.g. I have 4.19, 5.4, 5.10 and 5.13 installed, and I'm currently booting 5.4; I would hate that this changes every time one of the others is updated).

A possible fix might be to do something like this:
```
[...]
# get major version, e.g. "4.8" for "linux4.8"
major_version=$(echo $PKGNAME | cut -c 6-)

label="Void Linux with kernel ${major_version}"

# look for previous entry for this major kernel version
bootnum=$(efibootmgr | grep " $label$" | cut -c "5-8")

# get the boot order
# this is required because when in the next step the existing entry is removed,
# it is also removed from the order so it needs to be restored later
bootorder=$(efibootmgr | grep "^BootOrder: " |cut -c 12-)

# if existing, remove it and reuse the same number
if [ -n "$bootnum" ]; then
	args="$args -B -b $bootnum"
fi

# if there is a boot order, keep it as is
if [ -n "$bootorder" ]; then
	args="$args -o $bootorder"
fi

# create the new entry
efibootmgr -qc $args -L "$label" -l /vmlinuz-${VERSION} -u "${OPTIONS}"
```

Instead of calling the `post-remove/50-efibootmgr` hook, just tell efibootmgr to replace the entry. This also keeps the order in the same call to efibootmgr so you don't have to do that in a separate step anymore.