Add doas support to is_root_or_sudo_prefix

doas is not compatible with sudo flags. The codebase was checked for
sudo-specific uses of this function, but none were found, all cases were
in the form of `sudo <command>`. Replacing it with `doas <command>`
yields the same result.

lib/functions/host/host-utils.sh

@@ -96,6 +96,10 @@ function is_root_or_sudo_prefix() {
 		# sudo binary found in path, use it.
 		display_alert "EUID is not 0" "sudo binary found, using it" "debug"
 		__my_sudo_prefix="sudo"
+	elif [[ -n "$(command -v doas)" ]]; then
+		# doas binary found in path, use it.
+		display_alert "EUID is not 0" "doas binary found, using it" "debug"
+		__my_sudo_prefix="doas"
 	else
 		# No root and no sudo binary. Bail out
 		exit_with_error "EUID is not 0 and no sudo binary found - Please install sudo or run as root"