Recovery resource must be install to either boot or vendor_boot

... but not both.

Test: builds
Change-Id: I4bebb09632f49fddef25eadc2cad89f41f38178b
diff --git a/core/board_config.mk b/core/board_config.mk
index 457b3bf..fafd7b2 100644
--- a/core/board_config.mk
+++ b/core/board_config.mk
@@ -787,3 +787,10 @@
       Use BOARD_MOVE_RECOVERY_RESOURCES_TO_VENDOR_BOOT instead)
   endif
 endif
+
+ifeq (true,$(BOARD_MOVE_RECOVERY_RESOURCES_TO_VENDOR_BOOT))
+  ifeq (true,$(BOARD_USES_RECOVERY_AS_BOOT))
+    $(error BOARD_MOVE_RECOVERY_RESOURCES_TO_VENDOR_BOOT and BOARD_USES_RECOVERY_AS_BOOT cannot be \
+      both true. Recovery resources should be installed to either boot or vendor_boot, but not both)
+  endif
+endif