Install the update-payload-key in the recovery image as well.

The update-payload-key is required to verify the contents of the OTA in
recovery while sideloading an update.

Bug: 27178350
TEST=`make` builds a boot.img with the payload key in recovery.

(cherry picked from commit c6ebe9fcd7ca0c991f5ae0e711a251959d0d41f4)

Change-Id: I0128d7f684d32201e227acce798b25f12982eaaa
diff --git a/core/Makefile b/core/Makefile
index f267edc..3c360ac 100644
--- a/core/Makefile
+++ b/core/Makefile
@@ -715,6 +715,10 @@
 	$(hide) rm -f $@
 	$(hide) mkdir -p $(dir $@)
 	$(hide) openssl x509 -pubkey -noout -in $< > $@
+
+ALL_DEFAULT_INSTALLED_MODULES += $(TARGET_RECOVERY_ROOT_OUT)/etc/update_engine/update-payload-key.pub.pem
+$(TARGET_RECOVERY_ROOT_OUT)/etc/update_engine/update-payload-key.pub.pem: $(TARGET_OUT_ETC)/update_engine/update-payload-key.pub.pem
+	$(hide) cp -f $< $@
 endif
 endif