Add test_mainline_module option.

Bug: 165425972

Test: m HelloWorldTests
Change-Id: I6e60b3895328c4f7aef0bfb30dcdefc30ee1d8ed
diff --git a/java/androidmk.go b/java/androidmk.go
index 2c02e5f..a503d2a 100644
--- a/java/androidmk.go
+++ b/java/androidmk.go
@@ -166,6 +166,7 @@
 		if !BoolDefault(j.testProperties.Auto_gen_config, true) {
 			entries.SetString("LOCAL_DISABLE_AUTO_GENERATE_TEST_CONFIG", "true")
 		}
+		entries.AddStrings("LOCAL_TEST_MAINLINE_MODULES", j.testProperties.Test_mainline_modules...)
 	})
 
 	return entriesList
@@ -440,6 +441,7 @@
 		}
 		androidMkWriteExtraTestConfigs(a.extraTestConfigs, entries)
 		androidMkWriteTestData(a.data, entries)
+		entries.AddStrings("LOCAL_TEST_MAINLINE_MODULES", a.testProperties.Test_mainline_modules...)
 	})
 
 	return entriesList