Add property_contexts to SELINUX_DEPENDS.

This ensures there is a dependency between the root image
and changes to property_contexts file.
Signed-off-by: rpcraig <rpcraig@tycho.ncsc.mil>

Change-Id: I9bd2c3fc44015d6013e6a1f200f8abded271654f
diff --git a/core/Makefile b/core/Makefile
index 74883d4..a372103 100644
--- a/core/Makefile
+++ b/core/Makefile
@@ -343,7 +343,7 @@
 BUILT_RAMDISK_TARGET := $(PRODUCT_OUT)/ramdisk.img
 
 ifeq ($(HAVE_SELINUX),true)
-SELINUX_DEPENDS := sepolicy file_contexts seapp_contexts
+SELINUX_DEPENDS := sepolicy file_contexts seapp_contexts property_contexts
 endif
 
 # We just build this directly to the install location.