Allow mainline_arm64 to have product contents

The device currently targeted does not have a product partition.
Adding product-specific apps to it therefore trips up the artifact path
check for /system.

Workaround that by whitelisting /system/product/% for now. This should
be removed when the device has the right partitions.

Bug: 110072687
Test: build mainline_arm64
Merged-In: I54175bc51df5dfe82c64f66f255a2cea6ff9b9ab
Change-Id: I54175bc51df5dfe82c64f66f255a2cea6ff9b9ab