Allow cuttlefish auto targets to select a vehicle hal implementation

Bug: 148393911
Test: build and boot
Change-Id: Ib5a0f61b555eb5ac0085b67467f6ae3d0cf6f6f7
diff --git a/shared/auto/device.mk b/shared/auto/device.mk
index 30ff594..e0693e5 100644
--- a/shared/auto/device.mk
+++ b/shared/auto/device.mk
@@ -57,7 +57,10 @@
     vendor.rild.libpath=libcuttlefish-ril.so \
 
 # vehicle HAL
-PRODUCT_PACKAGES += android.hardware.automotive.vehicle@2.0-service
+ifeq ($(LOCAL_VHAL_PRODUCT_PACKAGE),)
+    LOCAL_VHAL_PRODUCT_PACKAGE := android.hardware.automotive.vehicle@2.0-service
+endif
+PRODUCT_PACKAGES += $(LOCAL_VHAL_PRODUCT_PACKAGE)
 
 # Broadcast Radio
 PRODUCT_PACKAGES += android.hardware.broadcastradio@2.0-service