fix: don't force the use of nix_2_4 for flakes when nix is new enough

nix-on-droid/default.nix

@@ -1,6 +1,6 @@
 # Copyright (c) 2019-2020, see AUTHORS. Licensed under MIT License, see LICENSE.
 
-{ bash, coreutils, nix, nix_2_4, runCommand }:
+{ bash, coreutils, lib, nix, nix_2_4, runCommand }:
 
 runCommand
   "nix-on-droid"
@@ -15,5 +15,5 @@ runCommand
       --subst-var-by bash "${bash}" \
       --subst-var-by coreutils "${coreutils}" \
       --subst-var-by nix "${nix}" \
-      --subst-var-by nix24 "${nix_2_4}"
+      --subst-var-by nixge24 "${if lib.versionAtLeast nix.version "2.4pre" then nix else nix_2_4}"
   ''

nix-on-droid/nix-on-droid.sh

@@ -28,7 +28,7 @@ function nixActivationPackage() {
     local extraArgs=("${@:2}" "${PASSTHROUGH_OPTS[@]}")
     local nix=nix
     if [[ -n "${FLAKE_CONFIG_URI}" ]]; then
-        nix=@nix24@/bin/nix
+        nix=@nixge24@/bin/nix
         extraArgs+=(--impure "${FLAKE_CONFIG_URI}.activationPackage")
     else
         extraArgs+=(--file "<nix-on-droid/modules>" activationPackage)