Fix host path for dexpreopted system server modules defined in Make.

Previously there was a discrepancy between the generated paths for
Soong modules that used "out/soong/system_server_jars" and Make modules
that used "out/system_server_jars". This happened because the default
output directory is $OUT/soong for the normal Soong config and jsut $OUT
for the reduced "null config" created by dexpreopt_gen.

As a result, class loader context for system server jars defined in Make
was referring to nonexistent jars, which caused non-fatal dex2oat errors
(the build was not broken, so the errors remained unnoticed):

  Failed to determine oat file name for dex location out/system_server_dexjars/[...]
  Could not open dex files from location: out/system_server_dexjars/[...]

Test: aosp_walleye-userdebug boots
Test: cherry-picked in master-arc-dev that has a Make system server jar
  arc-services, `lunch lunch cheets_x86-userdebug && m`, check that the
  generated dexpreopt.sh for arc-services contains paths starting with
  "out/soong/system_server_jars" rather than "out/system_server_jars".

Bug: 140712566
Change-Id: Ia7ea8ac383e32042c31d64971cdc8101ea3068cd
diff --git a/dexpreopt/dexpreopt.go b/dexpreopt/dexpreopt.go
index 0e1bfc6..f984966 100644
--- a/dexpreopt/dexpreopt.go
+++ b/dexpreopt/dexpreopt.go
@@ -47,6 +47,8 @@
 const SystemPartition = "/system/"
 const SystemOtherPartition = "/system_other/"
 
+var DexpreoptRunningInSoong = false
+
 // GenerateDexpreoptRule generates a set of commands that will preopt a module based on a GlobalConfig and a
 // ModuleConfig.  The produced files and their install locations will be available through rule.Installs().
 func GenerateDexpreoptRule(ctx android.PathContext, globalSoong *GlobalSoongConfig,
@@ -589,7 +591,14 @@
 // at that time (Soong processes the jars in dependency order, which may be different from the
 // the system server classpath order).
 func SystemServerDexJarHostPath(ctx android.PathContext, jar string) android.OutputPath {
-	return android.PathForOutput(ctx, "system_server_dexjars", jar+".jar")
+	if DexpreoptRunningInSoong {
+		// Soong module, just use the default output directory $OUT/soong.
+		return android.PathForOutput(ctx, "system_server_dexjars", jar+".jar")
+	} else {
+		// Make module, default output directory is $OUT (passed via the "null config" created
+		// by dexpreopt_gen). Append Soong subdirectory to match Soong module paths.
+		return android.PathForOutput(ctx, "soong", "system_server_dexjars", jar+".jar")
+	}
 }
 
 func contains(l []string, s string) bool {
diff --git a/java/dexpreopt.go b/java/dexpreopt.go
index fba0b97..4725b07 100644
--- a/java/dexpreopt.go
+++ b/java/dexpreopt.go
@@ -62,6 +62,10 @@
 	}
 }
 
+func init() {
+	dexpreopt.DexpreoptRunningInSoong = true
+}
+
 func (d *dexpreopter) dexpreoptDisabled(ctx android.BaseModuleContext) bool {
 	global := dexpreopt.GetGlobalConfig(ctx)