Fix building in Lineage 16.0

Change-Id: Ia7c66d469c69d9c4e9263feae7b48d40c09af155
diff --git a/Android.mk b/Android.mk
index 8ed4c6c..3b29c7a 100644
--- a/Android.mk
+++ b/Android.mk
@@ -15,7 +15,7 @@
 LOCAL_PATH := $(call my-dir)
 commands_TWRP_local_path := $(LOCAL_PATH)
 
-ifdef project-path-for
+ifneq ($(project-path-for),)
     ifeq ($(LOCAL_PATH),$(call project-path-for,recovery))
         PROJECT_PATH_AGREES := true
         BOARD_SEPOLICY_DIRS += $(call project-path-for,recovery)/sepolicy