axolotl: Don't let builds complete without vendor tree

* There is zero reason to ever build without blobs. We've even seen
  this situation with official builds from our servers. It's always
  better for a build to fail than it is for it to produce something
  that has no chance at working.

Change-Id: I4968795670c91f691e9ecdc0e4af62e16ba3a93a
(cherry picked from commit 98cd6f263cd61d6303669804847965e75ba89db5)
diff --git a/device.mk b/device.mk
index 22485de..c9e2bdd 100644
--- a/device.mk
+++ b/device.mk
@@ -13,7 +13,7 @@
 $(call inherit-product, $(SRC_TARGET_DIR)/product/updatable_apex.mk)
 
 # Inherit vendor blobs
-$(call inherit-product-if-exists, vendor/shift/axolotl/axolotl-vendor.mk)
+$(call inherit-product, vendor/shift/axolotl/axolotl-vendor.mk)
 
 # AAPT
 PRODUCT_AAPT_CONFIG := normal