Since commit dc5fc898f6 (Xcode: Set object file locations using
TARGET_TEMP_DIR, 2022-09-29, v3.25.0-rc1~64^2~1), `xcodebuild clean`
does not remove the object files in our explicit `TARGET_TEMP_DIR`
because it is not under the `SYMROOT`. Put it there.
Fixes: #24096