Add WithDexpreopt soong variable

Test: m selinux_policy on sc-arc
Change-Id: I9e8ba5746e4648a04fe4d8fbe5d3403ba06b5914
diff --git a/android/config.go b/android/config.go
index 0de8928..e335de0 100644
--- a/android/config.go
+++ b/android/config.go
@@ -1005,6 +1005,10 @@
 	return ioutil.ReadFile(absolutePath(path.String()))
 }
 
+func (c *deviceConfig) WithDexpreopt() bool {
+	return c.config.productVariables.WithDexpreopt
+}
+
 func (c *config) FrameworksBaseDirExists(ctx PathContext) bool {
 	return ExistentPathForSource(ctx, "frameworks", "base", "Android.bp").Valid()
 }