Prep D8 default instead of CompatDX in build/soong

Bug: 69329508
Test: m checkbuild tests
Change-Id: Ibaa2d787c644cf25104af78305a6eed16028dcf0
diff --git a/java/java.go b/java/java.go
index 9b345fd..05d38f2 100644
--- a/java/java.go
+++ b/java/java.go
@@ -677,7 +677,7 @@
 	// Store the list of .java files that was passed to javac
 	j.compiledJavaSrcs = uniqueSrcFiles
 	j.compiledSrcJars = srcJars
-	fullD8 := ctx.AConfig().IsEnvTrue("USE_D8_DESUGAR")
+	fullD8 := ctx.Config().UseD8Desugar()
 
 	enable_sharding := false
 	if ctx.Device() && !ctx.Config().IsEnvFalse("TURBINE_ENABLED") {