Error if BOARD_VNDK_VERSION=PLATFORM_VNDK_VERSION

"BOARD_VNDK_VERSION := current" should be used instead.

Bug: 159866756
Test: manual
Change-Id: I854ca9c0fa195ab4bbb468a1343ef4fa28ac9258
diff --git a/core/board_config.mk b/core/board_config.mk
index ae1614f..e0bc2f4 100644
--- a/core/board_config.mk
+++ b/core/board_config.mk
@@ -593,6 +593,9 @@
 endef
 
 ifdef BOARD_VNDK_VERSION
+  ifeq ($(BOARD_VNDK_VERSION),$(PLATFORM_VNDK_VERSION))
+    $(error BOARD_VNDK_VERSION is equal to PLATFORM_VNDK_VERSION; use BOARD_VNDK_VERSION := current))
+  endif
   ifneq ($(BOARD_VNDK_VERSION),current)
     $(call check_vndk_version,$(BOARD_VNDK_VERSION))
   endif