Add libextension_flat_tensor.a to build_apple_frameworks.sh (#10758)

Fix apple build

Author: kirklandsign

scripts/build_apple_frameworks.sh

@@ -30,6 +30,7 @@ libexecutorch.a,\
 libexecutorch_core.a,\
 libextension_apple.a,\
 libextension_data_loader.a,\
+libextension_flat_tensor.a,\
 libextension_module.a,\
 libextension_tensor.a,\
 :$HEADERS_PATH"