Add dir.system = /product/app/ entry

This is a fallback for binaries in APKs being launched.

Bug: 160433462
Test: atest --host linkerconfig_diff_test
Change-Id: I3979b22994d7c801952c13d8bbfa013da78b69e2
(cherry picked from commit 2a62a40819fbfb243c1040cd807f5df5d14c4903)
1 file changed