Add new module type for adb_keys.

Bug: 371107666
Change-Id: Ibaee842f807bc829ca615d5754851e03a4aa5548
Test: CIs
diff --git a/android/variable.go b/android/variable.go
index 1aaa70a..51a239d 100644
--- a/android/variable.go
+++ b/android/variable.go
@@ -522,6 +522,8 @@
 	DeviceProductCompatibilityMatrixFile   []string `json:",omitempty"`
 
 	PartitionVarsForSoongMigrationOnlyDoNotUse PartitionVariables
+
+	AdbKeys *string `json:",omitempty"`
 }
 
 type PartitionQualifiedVariablesType struct {