Use BOARD_USES_VENDORIMAGE to detect vendor image presence - DO NOT MERGE

When building without vendor/... in the tree, we won't be creating a
vendorimage, so BOARD_VENDORIMAGE_FILE_SYSTEM_TYPE won't be defined. But
we still need to use the vendor image that will be present.

Bug: 31545062
Bug: 30040825
Change-Id: I756adc615aea11da60da4d3a4568caca9fed93ab
(cherry picked from commit 15366542)

CleanSpec.mk

@@ -56,3 +56,4 @@ $(call add-clean-step, rm -rf $(PRODUCT_OUT)/recovery/root/default.prop)
 $(call add-clean-step, rm -rf $(PRODUCT_OUT)/obj/EXECUTABLES/lmkd_intermediates/import_includes)
 $(call add-clean-step, rm -rf $(PRODUCT_OUT)/obj/SHARED_LIBRARIES/libsysutils_intermediates/import_includes)
 $(call add-clean-step, rm -rf $(PRODUCT_OUT)/system/bin/grep $(PRODUCT_OUT)/system/bin/toolbox)
+$(call add-clean-step, rm -rf $(PRODUCT_OUT)/root/vendor)

rootdir/Android.mk

@@ -125,7 +125,7 @@ LOCAL_POST_INSTALL_CMD := mkdir -p $(addprefix $(TARGET_ROOT_OUT)/, \
     ln -sf /system/etc $(TARGET_ROOT_OUT)/etc; \
     ln -sf /sys/kernel/debug $(TARGET_ROOT_OUT)/d; \
     ln -sf /storage/self/primary $(TARGET_ROOT_OUT)/sdcard
-ifdef BOARD_VENDORIMAGE_FILE_SYSTEM_TYPE
+ifdef BOARD_USES_VENDORIMAGE
   LOCAL_POST_INSTALL_CMD += ; mkdir -p $(TARGET_ROOT_OUT)/vendor
 else
   LOCAL_POST_INSTALL_CMD += ; ln -sf /system/vendor $(TARGET_ROOT_OUT)/vendor