shell is available to the recovery mode

Bug: 63673171
Test: `adb reboot recovery; adb devices` shows the device ID
Test: `adb root && adb shell` works
Change-Id: I89ceb2c8d3519b2e4793830b86aed8f4b7af1572
diff --git a/Android.bp b/Android.bp
index 2bca561..1f846b0 100644
--- a/Android.bp
+++ b/Android.bp
@@ -121,6 +121,7 @@
 cc_binary {
     name: "sh",
     defaults: ["sh-defaults"],
+    recovery_available: true,
 }
 
 cc_binary {