nixos-rebuild: Support passing e.g. '-j8'

Where there is no space between '-j' and the number.

nixos/modules/installer/tools/nixos-rebuild.sh

@@ -52,13 +52,13 @@ while [ "$#" -gt 0 ]; do
         repair=1
         extraBuildFlags+=("$i")
         ;;
-      --show-trace|--no-build-hook|--keep-failed|-K|--keep-going|-k|--verbose|-v|-vv|-vvv|-vvvv|-vvvvv|--fallback|--repair|--no-build-output|-Q)
-        extraBuildFlags+=("$i")
-        ;;
       --max-jobs|-j|--cores|-I)
         j="$1"; shift 1
         extraBuildFlags+=("$i" "$j")
         ;;
+      --show-trace|--no-build-hook|--keep-failed|-K|--keep-going|-k|--verbose|-v|-vv|-vvv|-vvvv|-vvvvv|--fallback|--repair|--no-build-output|-Q|-j*)
+        extraBuildFlags+=("$i")
+        ;;
       --option)
         j="$1"; shift 1
         k="$1"; shift 1