Package Dexpreopt files

Dexpreopt files started to be missed from Soong defined system images.
Package those files so they can be added into the system image in the
same way with KATI system image.

Bug: 370352548
Test: Soong defined system image build succeeded
Change-Id: I1b665b9a891d89d3f042c0ad8a4ffca6cd567b2e
diff --git a/apex/builder.go b/apex/builder.go
index 8427719..e8a4078 100644
--- a/apex/builder.go
+++ b/apex/builder.go
@@ -592,6 +592,7 @@
 			}
 			a.extraInstalledFiles = append(a.extraInstalledFiles, installedFile)
 			a.extraInstalledPairs = append(a.extraInstalledPairs, installPair{install.OutputPathOnHost, installedFile})
+			ctx.PackageFile(install.InstallDirOnDevice, install.InstallFileOnDevice, install.OutputPathOnHost)
 		}
 		if performInstalls {
 			for _, dexJar := range fi.systemServerDexJars {