Add /system/product/* paths to permitted paths

As linker doesn't resolve paths in permitted paths, /system/product
variants should be added to support devices having product partition
under /system.

Bug: 110286945
Test: m -j succeeds on taimen and libraries under /system can dlopen
libraries under /system/product/apps

Change-Id: Icd102d44511702e4ec66c07a367b59c3d9700a44