makefile: fix potential bug

Copy first dependency, not all of them.

Allthough there is a distinction in Makefile between $^
and $<, there's no difference in the case that is fixed
as of writing.

This commit is just to clearly show a drive-by fix, before
the next commit.

Signed-off-by: Øyvind Harboe <[email protected]>

Author: oharboe

flow/Makefile

@@ -743,7 +743,7 @@ $(GDS_MERGED_FILE): $(RESULTS_DIR)/6_final.def $(OBJECTS_DIR)/klayout.lyt $(GDSO
 $(RESULTS_DIR)/6_final.v: $(LOG_DIR)/6_report.log
 
 $(GDS_FINAL_FILE): $(GDS_MERGED_FILE)
-	cp $^ $@
+	cp $< $@
 
 .PHONY: drc
 drc: $(REPORTS_DIR)/6_drc.lyrdb