flowy: avoid invoking no-op efibootmgr operations

hosts/by-name/flowy/default.nix

@@ -45,11 +45,12 @@
           bootCurrent=''${bootCurrent/BootCurrent: /}
           bootOrder=$(echo "$efi" | grep '^BootOrder: ')
           bootOrder=''${bootOrder/BootOrder: /}
-          # prepend the current boot entry to the boot order...
-          newBootOrder="$bootCurrent,$bootOrder"
-          # but in a way that's idempotent :)
-          newBootOrder=''${newBootOrder/$bootCurrent,$bootCurrent/$bootCurrent}
-          (set -x; efibootmgr -o "$newBootOrder")
+          if ! [[ "$bootOrder" =~ ^"$bootCurrent", ]]; then
+            # booted entry was not the default,
+            # so prepend it to the boot order:
+            newBootOrder="$bootCurrent,$bootOrder"
+            (set -x; efibootmgr -o "$newBootOrder")
+          fi
         '';
       };
     in lib.getExe makeDefaultBootEntry;