common: Allow custom vendor to override properties

Test case: override ro.adb.secure in vendor/extra/product.mk
Before this patch, the override would not affect the resulting
property.

Change-Id: I0deb8a6865030b09ed6ba0ede1658319ca033e67

config/common.mk

@@ -1,3 +1,6 @@
+# Allow vendor/extra to override any property by setting it first
+$(call inherit-product-if-exists, vendor/extra/product.mk)
+
 PRODUCT_BRAND ?= LineageOS
 
 PRODUCT_BUILD_PROP_OVERRIDES += BUILD_UTC_DATE=0
@@ -367,5 +370,3 @@ endif
 
 -include $(WORKSPACE)/build_env/image-auto-bits.mk
 -include vendor/lineage/config/partner_gms.mk
-
-$(call inherit-product-if-exists, vendor/extra/product.mk)