Fix logging in as incorrect user if phases kexec is not set

When executing nixos-anywhere --phases disko myuser@<ip> for example we
must assume that kexec has already been run and that the target user
changed to root now. This will force nixos-anywhere to log in as root
user if the kexec phase is not present.

Co-authored-by: Qubasa <consulting@qube.email>

Author: Mic92

src/nixos-anywhere.sh

@@ -1016,6 +1016,12 @@ main() {
   sshUser=$(echo "$sshSettings" | awk '/^user / { print $2 }')
   sshHost="${sshConnection//*@/}"
 
+  # If kexec phase is not present, we assume kexec has already been run
+  # and change the user to root@<sshHost> for the rest of the script.
+  if [[ ${phases[kexec]} != 1 ]]; then
+    sshConnection="root@${sshHost}"
+  fi
+
   uploadSshKey
 
   importFacts