Don't dexpreopt when compile_dex but not installable

Modules shouldn't be dexpreopted and possibly stripped when
compile_dex is set but installable is not set.  This matches the
previous behavior when the dexpreopt rules were in Make.

Bug: 121317615
Test: dexpreopt_test.go
Change-Id: I6f80b7b37a990c475b91aa5d98a19a3baa85eb1b

java/dexpreopt.go

@@ -28,10 +28,11 @@ import (
 type dexpreopter struct {
 	dexpreoptProperties DexpreoptProperties
 
-	installPath  android.OutputPath
-	isPrivApp    bool
-	isSDKLibrary bool
-	isTest       bool
+	installPath   android.OutputPath
+	isPrivApp     bool
+	isSDKLibrary  bool
+	isTest        bool
+	isInstallable bool
 
 	builtInstalled []string
 }
@@ -74,6 +75,10 @@ func (d *dexpreopter) dexpreoptDisabled(ctx android.ModuleContext) bool {
 		return true
 	}
 
+	if !d.isInstallable {
+		return true
+	}
+
 	// TODO: contains no java code
 
 	return false