stdlib: Fixing resources.json caching for multi-user envs

The downloader briefly caches the resources.json file in "/tmp". This
works fine if the system only has one user, but in a system supporting
many users, where "/tmp" is shared, there were permission issues when a
user tried to access a resources.json cache from another user. To
resolve this the uid of the user is appended to the filename.

Change-Id: Iba8ab12cd7054c2f5636e444ac0f1f8f73fedc89
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/58489
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>
Maintainer: Jason Lowe-Power <power.jg@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>

src/python/gem5/resources/downloader.py

@@ -80,7 +80,8 @@ def _get_resources_json_at_url(url: str, use_caching: bool = True) -> Dict:
 
     file_path = os.path.join(
         gettempdir(),
-        f"gem5-resources-{hashlib.md5(url.encode()).hexdigest()}.base64",
+        f"gem5-resources-{hashlib.md5(url.encode()).hexdigest()}"
+        f"-{str(os.getuid())}.base64",
     )
 
     # We apply a lock on the resources file for when it's downloaded, or