ATest: GTest auto gen config support run-test-as.

Feature request from developer, support setting uid in makefile.

Bug: 113359343
Test: apply aosp/757329
      make -j hello_world_test_mk (w/ UID setting in config)
      make -j hello_world_test_mk2 (w/o UID setting in config)
      check test config of host's hello_world_test_mk (w/o UID setting in config)

Change-Id: I167c737098fa906e401769c6a8838f46b03bd33c