vendor/lineage: Depend on existing definition of empty

Defined and marked readonly in build/make here:
7ddc50a066/common/core.mk (L46)

Change-Id: Ic233f0d41d03b28beb8d96c68692271d959fa188

build/core/utils.mk

@@ -1,6 +1,6 @@
 # vars for use by utils
-empty :=
-space := $(empty) $(empty)
+# the following are already defined in build/make:
+# empty space comma newline pound backslash
 colon := $(empty):$(empty)
 underscore := $(empty)_$(empty)