Add temporary system property checks in addition in addition to flag checks.

This was agreed on to enable dogfood testing on P9 without enabling the full
feature in QPR3. https://docs.google.com/document/d/1ZItkXfyKO2e235-EdisHASE6Dcl2hqATnieo6aJrsbY/edit?tab=t.0#bookmark=id.64wdrt989i3r

Test: PackageInstallerArchiveTest
Bug: 315461548
Change-Id: I3d73930822e5dcd6c945f6eeb2faae5952498ec3