Don't add flattened files apex as dependencies of an image apex

The image apex does not need all the files that make up a flattened
apex.

Bug: 254205429
Test: go tests
Change-Id: I7c574c5b30b55ab6d1b3981ee26d168c2f2427c4
diff --git a/apex/androidmk.go b/apex/androidmk.go
index b76f6bd..aadccb7 100644
--- a/apex/androidmk.go
+++ b/apex/androidmk.go
@@ -317,14 +317,14 @@
 func (a *apexBundle) androidMkForType() android.AndroidMkData {
 	return android.AndroidMkData{
 		Custom: func(w io.Writer, name, prefix, moduleDir string, data android.AndroidMkData) {
-			moduleNames := []string{}
 			apexType := a.properties.ApexType
-			if a.installable() {
-				apexName := proptools.StringDefault(a.properties.Apex_name, name)
-				moduleNames = a.androidMkForFiles(w, name, apexName, moduleDir, data)
-			}
 
 			if apexType == flattenedApex {
+				var moduleNames []string = nil
+				if a.installable() {
+					apexName := proptools.StringDefault(a.properties.Apex_name, name)
+					moduleNames = a.androidMkForFiles(w, name, apexName, moduleDir, data)
+				}
 				// Only image APEXes can be flattened.
 				fmt.Fprintln(w, "\ninclude $(CLEAR_VARS)  # apex.apexBundle.flat")
 				fmt.Fprintln(w, "LOCAL_PATH :=", moduleDir)
@@ -366,7 +366,7 @@
 				}
 
 				android.AndroidMkEmitAssignList(w, "LOCAL_OVERRIDES_MODULES", a.overridableProperties.Overrides)
-				a.writeRequiredModules(w, moduleNames)
+				a.writeRequiredModules(w, nil)
 
 				fmt.Fprintln(w, "include $(BUILD_PREBUILT)")