Support apk for product_variables.debuggable

Bug: 365707065
Test: m FactoryOtaPrebuilt
Change-Id: I880b9d48b52d49cbf8c1eca6a67d3ffadc8ea0fc
diff --git a/android/variable.go b/android/variable.go
index 9026f93..8c004df 100644
--- a/android/variable.go
+++ b/android/variable.go
@@ -121,6 +121,7 @@
 		// are used for dogfooding and performance testing, and should be as similar to user builds
 		// as possible.
 		Debuggable struct {
+			Apk             *string
 			Cflags          []string
 			Cppflags        []string
 			Init_rc         []string