symlink_outputs: Add .KATI_SYMLINK_OUTPUTS to build/make/core

Test: m
Bug: 160568334

Change-Id: Ie6fb4f16bb77845787d277857e17e6aac0a8c11a
diff --git a/core/Makefile b/core/Makefile
index 9471148..4075c49 100644
--- a/core/Makefile
+++ b/core/Makefile
@@ -2384,6 +2384,7 @@
 	  exit 1; \
 	fi
 	ln -sfn $2 $1
+$1: .KATI_SYMLINK_OUTPUTS := $1
 )
 $1
 endef