fix imports, make emulator run on system architecture

template/devenv.nix

@@ -30,13 +30,14 @@
       version = [ "27.1.12297006" ];
     };
   };
-  enterShell = ''
+  # The emulator's bundled libs are only needed on Linux; macOS uses DYLD paths.
+  enterShell = lib.optionalString pkgs.stdenv.isLinux ''
     export LD_LIBRARY_PATH=$ANDROID_HOME/emulator/lib64:$LD_LIBRARY_PATH
   '';
+  # Use a system image matching the host CPU (arm64 on Apple Silicon, x86_64 elsewhere).
   scripts.create-avd.exec = ''
-    if [ ! -f .avd-created ]; then
-      avdmanager create avd -n "Pixel_5_API34" -k "system-images;android-34;google_apis_playstore;x86_64" -d "pixel_5";
-      touch .avd-created;
+    if ! avdmanager list avd -c | grep -qx "Pixel_5_API34"; then
+      echo no | avdmanager create avd -n "Pixel_5_API34" -k "system-images;android-34;google_apis_playstore;${if pkgs.stdenv.hostPlatform.isAarch64 then "arm64-v8a" else "x86_64"}" -d "pixel_5"
     fi
   '';
  <@endif>