Build ramdisk with soong

This is the first step to build the ramdisk, it still has some diffs
with with the make-generated ramdisk though.

Bug: 378146476
Test: m soong_generated_ramdisk_filesystem_test
Change-Id: I767ea9d09e4d6413c2ec5af3120595e2001c9bb7
diff --git a/android/variable.go b/android/variable.go
index c6a1b0a..89d90c2 100644
--- a/android/variable.go
+++ b/android/variable.go
@@ -606,10 +606,20 @@
 	BoardExt4ShareDupBlocks        string `json:",omitempty"`
 	BoardFlashLogicalBlockSize     string `json:",omitempty"`
 	BoardFlashEraseBlockSize       string `json:",omitempty"`
-	BoardUsesRecoveryAsBoot        bool   `json:",omitempty"`
 	ProductUseDynamicPartitionSize bool   `json:",omitempty"`
 	CopyImagesForTargetFilesZip    bool   `json:",omitempty"`
 
+	// Boot image stuff
+	ProductBuildBootImage           bool   `json:",omitempty"`
+	ProductBuildInitBootImage       bool   `json:",omitempty"`
+	BoardUsesRecoveryAsBoot         bool   `json:",omitempty"`
+	BoardPrebuiltBootimage          string `json:",omitempty"`
+	BoardPrebuiltInitBootimage      string `json:",omitempty"`
+	BoardBootimagePartitionSize     string `json:",omitempty"`
+	BoardInitBootimagePartitionSize string `json:",omitempty"`
+	BoardBootHeaderVersion          string `json:",omitempty"`
+
+	// Avb (android verified boot) stuff
 	BoardAvbEnable          bool                                `json:",omitempty"`
 	BoardAvbAlgorithm       string                              `json:",omitempty"`
 	BoardAvbKeyPath         string                              `json:",omitempty"`