Revert^2 "Preopt APEX system server jars."

This reverts commit 92346c4832.

Reason for revert: Fixed build error.

The build error is fixed by ag/15841934. This CL remains unchanged. This
CL will be submitted AFTER ag/15841934 is submitted.

Bug: 200024131
Test: 1. Patch this CL and ag/15841934 into internal master.
  2. sudo vendor/google/build/build_test.bash

Change-Id: I5f2b8357846fc7dda56e25ebe6ffb095e8047ec8

java/androidmk.go

@@ -61,7 +61,13 @@ func (library *Library) AndroidMkEntries() []android.AndroidMkEntries {
 	var entriesList []android.AndroidMkEntries
 
 	if library.hideApexVariantFromMake {
-		// For a java library built for an APEX we don't need Make module
+		// For a java library built for an APEX, we don't need a Make module for itself. Otherwise, it
+		// will conflict with the platform variant because they have the same module name in the
+		// makefile. However, we need to add its dexpreopt outputs as sub-modules, if it is preopted.
+		dexpreoptEntries := library.dexpreopter.AndroidMkEntriesForApex()
+		if len(dexpreoptEntries) > 0 {
+			entriesList = append(entriesList, dexpreoptEntries...)
+		}
 		entriesList = append(entriesList, android.AndroidMkEntries{Disabled: true})
 	} else if !library.ApexModuleBase.AvailableFor(android.AvailableToPlatform) {
 		// Platform variant.  If not available for the platform, we don't need Make module.