Add prebuilt_boot_image and add boot_images to sdk

Bug: 177892522
Test: m nothing
Change-Id: I640359acd6840507f32d7034c97d4d1c7ff591e9
diff --git a/sdk/Android.bp b/sdk/Android.bp
index 8a3119c..6e49c6d 100644
--- a/sdk/Android.bp
+++ b/sdk/Android.bp
@@ -20,6 +20,7 @@
         "update.go",
     ],
     testSrcs: [
+        "boot_image_sdk_test.go",
         "bp_test.go",
         "cc_sdk_test.go",
         "exports_test.go",