vendor: add TARGET_NEEDS_HWC_ONFIRSTREF option

Change-Id: I1cb20129af69f641107c2b552cfd69eecfe65d64
diff --git a/build/soong/android/variable.go b/build/soong/android/variable.go
index 11569a3..75da6a4 100644
--- a/build/soong/android/variable.go
+++ b/build/soong/android/variable.go
@@ -1,6 +1,10 @@
 package android
 type Product_variables struct {
+	TargetNeedsHWCOnFirstRef struct {
+		Cflags []string
+	}
 }
 
 type ProductVariables struct {
+	TargetNeedsHWCOnFirstRef  *bool `json:",omitempty"`
 }