Add unit_test test option in test configs

This change allows a test (native, java, rust or python) to be included
in host-unit-tests suite when test option `unit_test` is set to true.

Bug: 172006742
Test: m host-unit-tests
Change-Id: I69d3eb5b51198c549e2e6914ceac3a4fc33c3cf2

java/androidmk.go

@@ -160,6 +160,9 @@ func (j *Test) AndroidMkEntries() []android.AndroidMkEntries {
 			entries.SetString("LOCAL_DISABLE_AUTO_GENERATE_TEST_CONFIG", "true")
 		}
 		entries.AddStrings("LOCAL_TEST_MAINLINE_MODULES", j.testProperties.Test_mainline_modules...)
+		if Bool(j.testProperties.Test_options.Unit_test) {
+			entries.SetBool("LOCAL_IS_UNIT_TEST", true)
+		}
 	})
 
 	return entriesList