Specify bootconfig property in vendor_boot.img

bootconfig is a path to the text file, created based on
`INTERNAL_BOOTCONFIG` and `INTERNAL_BOOTCONFIG_FILE`. This is done by
auto generating a newly introduced bootconfig module. The
output file of the genrule module is passed as a property to the
vendor_boot.img module.

Test: Inspect the content of the generated vendor-bootconfig.img file
Test: Inspect the ninja command of the autogen vendor_boot.img
Bug: 379945468
Change-Id: I9c693de681e6dad7399f80df05825cce9b0c1c22
diff --git a/android/variable.go b/android/variable.go
index 36ddc1c..5dd9b29 100644
--- a/android/variable.go
+++ b/android/variable.go
@@ -629,6 +629,8 @@
 	InitBootSecurityPatch           string   `json:",omitempty"`
 	BoardIncludeDtbInBootimg        bool     `json:",omitempty"`
 	InternalKernelCmdline           []string `json:",omitempty"`
+	InternalBootconfig              []string `json:",omitempty"`
+	InternalBootconfigFile          string   `json:",omitempty"`
 
 	// Avb (android verified boot) stuff
 	BoardAvbEnable          bool                                `json:",omitempty"`