Build test-runner/tests

Previous change e254526f0fe5d22681555bd4a00b7ee96fee1dc1 inadvertently
removed the line to include the tests/Android.mk file.

Bug: 30188076
Test: make checkbuild
Change-Id: Ia0ba14a70d2232d464420265a7a5f9c4dde3661b
1 file changed