This variable helps the EdgeTPU components to build different
targets per target chip accordingly.
Bug: 192096682
Test: tested on local Oriole.
Change-Id: I3de4082148392b184ed7e7e40de3fa93cbfe845d
Bug: 190331327
Bug: 190331548
Bug: 189895600
Bug: 190331108
Bug: 182524105
Bug: 183935302
Test: build ROM and check if the modules and sepolicy are still there
Change-Id: Id28ac2094e14051defe0401055d862c6353194f7