Adapt build_chd_utils.py for use with Python versions below 3.10. am: d0cd0acbd2

Original change: https://android-review.googlesource.com/c/platform/tools/treble/+/3016598

Change-Id: I24193b0f2c7789f154c0ee93bb6653757f731724
Signed-off-by: Automerger Merge Worker <[email protected]>