Dexpreopt standalone system server jars from prebuilts.

This change adds support for dexpreopting standalone system server
jars from prebuilts.

Bug: 203198541
Test: -
  1. Add a standalone system server jar (e.g., by patching
     aosp/1906158)
  2. Build and drop a module SDK and an APEX.
  3. Build a system image from prebuilts.
  4. See the odex and vdex files generated in
     $ANDROID_PRODUCT_OUT/system/framework/oat/
Change-Id: I8f4eaed10a1053cd560b8583efa12dc495f58db1
diff --git a/java/dexpreopt.go b/java/dexpreopt.go
index 3158450..edb6984 100644
--- a/java/dexpreopt.go
+++ b/java/dexpreopt.go
@@ -115,6 +115,11 @@
 	return !apexInfo.IsForPlatform()
 }
 
+func forPrebuiltApex(ctx android.BaseModuleContext) bool {
+	apexInfo := ctx.Provider(android.ApexInfoProvider).(android.ApexInfo)
+	return apexInfo.ForPrebuiltApex
+}
+
 func moduleName(ctx android.BaseModuleContext) string {
 	// Remove the "prebuilt_" prefix if the module is from a prebuilt because the prefix is not
 	// expected by dexpreopter.
@@ -134,7 +139,9 @@
 		return true
 	}
 
-	if !ctx.Module().(DexpreopterInterface).IsInstallable() {
+	// If the module is from a prebuilt APEX, it shouldn't be installable, but it can still be
+	// dexpreopted.
+	if !ctx.Module().(DexpreopterInterface).IsInstallable() && !forPrebuiltApex(ctx) {
 		return true
 	}