Adding a brillo_tests task.

Places whitelisted brillo tests and the whitelist itself
in a zip when run.

BUG: 27385399
Change-Id: I93c2ea8cc521292a6de811bb47bc87a727edd21f
TEST: manual make dist brillo_tests, confirmed desired files were in zip.
diff --git a/core/ninja.mk b/core/ninja.mk
index 2878514..df35965 100644
--- a/core/ninja.mk
+++ b/core/ninja.mk
@@ -27,6 +27,7 @@
 	ECLIPSE-% \
 	PRODUCT-% \
 	boottarball-nodeps \
+	brillo_tests \
 	btnod \
 	build-art% \
 	build_kernel-nodeps \