use CACHE_DIR constant

frigate/app.py

@@ -41,7 +41,7 @@ class FrigateApp():
         tmpfs_size = self.config.save_clips.tmpfs_cache_size
         if tmpfs_size:
              logger.info(f"Creating tmpfs of size {tmpfs_size}")
-             rc = os.system(f"mount -t tmpfs -o size={tmpfs_size} tmpfs /tmp/cache")
+             rc = os.system(f"mount -t tmpfs -o size={tmpfs_size} tmpfs {CACHE_DIR}")
              if rc != 0:
                  logger.error(f"Failed to create tmpfs, error code: {rc}")