Correct link type for module stubs

Module stubs compile against module_current, so any module depending on
them had to compile against module_current (or broader) too. Treat them
as the API surface the stubs are for.

Bug: 157010342
Test: m
Change-Id: I49b9082dc1b5afe6c22e94126e574dd8061f0f39

java/java.go

@@ -843,6 +843,10 @@ func (m *Module) getLinkType(name string) (ret linkType, stubs bool) {
 		return javaSystem, true
 	}
 
+	if stub, linkType := moduleStubLinkType(name); stub {
+		return linkType, true
+	}
+
 	ver := m.sdkVersion()
 	switch ver.kind {
 	case sdkCore: