fix: a platform's own data trees leave its pack

The platform layer names data trees for its systems: retroarch.yml carries dolphin-sys and ppsspp-assets, and Lakka inherits them, while Lakka's core packages install both trees into the system directory. A profile records that with installed_on on its data directory, and the pack and the install manifest now leave those trees out for that platform.

scripts/generate_pack.py

@@ -33,6 +33,7 @@ from pathlib import Path
 sys.path.insert(0, os.path.dirname(__file__))
 from common import resolve_platform_cores as _platform_cores
 from common import (
+    installed_data_refs,
     platform_arg,
     require_directory,
     target_listing_line,
@@ -400,6 +401,8 @@ def _data_directory_members(
             ref_key = dd.get("ref", "")
             if not ref_key or not data_registry or ref_key not in data_registry:
                 continue
+            if ref_key in installed_data_refs(platform_name):
+                continue
             entry = data_registry[ref_key]
             allowed = entry.get("for_platforms")
             if allowed and platform_name not in allowed: