bullhead: only build vendor/ code when non-aosp

Test: lunch aosp_bullhead-userdebug;
  rm -r vendor/lge/bullhead/fingerprint/; make;
Bug: 33251689
Change-Id: If961f5db6b05ed1c575eb949c196847563554ffa
diff --git a/device.mk b/device.mk
index f972525..4b1c0a0 100644
--- a/device.mk
+++ b/device.mk
@@ -488,4 +488,4 @@
 
 $(call inherit-product-if-exists, hardware/qcom/msm8994/msm8992.mk)
 $(call inherit-product-if-exists, vendor/qcom/gpu/msm8994/msm8994-gpu-vendor.mk)
-$(call inherit-product, vendor/lge/bullhead/fingerprint/device/device.mk)
+$(call inherit-product-if-exists, vendor/lge/bullhead/fingerprint/device/device.mk)