Prevent abuse of property overrides

To prevent abuse of PRODUCT_*PROPERTY_OVERRIDES and
ADDITIONAL*PROPERTIES, the following rules should be applied.

- Mark PRODUCT_*PROPERTY_OVERRIDES readonly after reading product
 specs.
- Disallow any changes on ADDITIONAL*PROPERTIES from product specs
 and BoardConfig.mk.
- Mark ADDITIONAL*PROPERTIES readonly before reading Android.mk
 files.

Test: building succeeded on marlin-userdebug.
Bug: 34116668
Change-Id: I93d8de086ec85ba787165a156bdcc7df04310be1
(cherry picked from commit 294286d9)