Support apex_test.

Bug: 249744489
Test: Manual and unit test.
Change-Id: I866debf7ffee54a0f4649b5e5425a8e3cc3042a1
diff --git a/android/module.go b/android/module.go
index 5aecb05..b41a898 100644
--- a/android/module.go
+++ b/android/module.go
@@ -928,6 +928,8 @@
 	Tags bazel.StringListAttribute
 
 	Applicable_licenses bazel.LabelListAttribute
+
+	Testonly *bool
 }
 
 // constraintAttributes represents Bazel attributes pertaining to build constraints,