config: build adb_root not on user

Inspired by https://github.com/DerpFest-AOSP/vendor_derp/commit/0e38790e2000cfe592c79b7cad1e0fe738cfa473

config/common.mk

@@ -13,6 +13,10 @@ PRODUCT_SYSTEM_DEFAULT_PROPERTIES += \
     ro.com.google.clientidbase=$(PRODUCT_GMS_CLIENTID_BASE)
 endif
 
+ifneq ($(TARGET_BUILD_VARIANT),user)
+PRODUCT_PACKAGES += adb_root
+endif
+
 ifeq ($(TARGET_BUILD_VARIANT),eng)
 # Disable ADB authentication
 PRODUCT_SYSTEM_DEFAULT_PROPERTIES += ro.adb.secure=0