AirArkanoid: Fix python3 on Windows (#155)

Co-authored-by: hedger <hedger@users.noreply.github.com>

application.fam

@@ -12,7 +12,7 @@ App(
     fap_extbuild=(
         ExtFile(
             path="${FAP_SRC_DIR}/assets",
-            command="python3 ${FAP_SRC_DIR}/engine/scripts/sprite_builder.py ${FAP_SRC_DIR.abspath}/sprites ${TARGET.abspath}/sprites",
+            command="${PYTHON3} ${FAP_SRC_DIR}/engine/scripts/sprite_builder.py ${FAP_SRC_DIR.abspath}/sprites ${TARGET.abspath}/sprites",
         ),
     ),
 )