feat: run timing scripts in parallel and print summary at the end

Makefile

diff --git a/Makefile b/Makefile
index 7a99ad4..8f049f4 100644
--- a/Makefile
+++ b/Makefile
@@ -318,7 +318,9 @@
 	
 .PHONY: caravel-sta
 caravel-sta: ./env/spef-mapping.tcl
-	@$(MAKE) -C $(TIMING_ROOT) -f $(TIMING_ROOT)/timing.mk caravel-timing-typ
-	@$(MAKE) -C $(TIMING_ROOT) -f $(TIMING_ROOT)/timing.mk caravel-timing-fast
-	@$(MAKE) -C $(TIMING_ROOT) -f $(TIMING_ROOT)/timing.mk caravel-timing-slow
+	@$(MAKE) -C $(TIMING_ROOT) -f $(TIMING_ROOT)/timing.mk caravel-timing-typ -j3
+	@$(MAKE) -C $(TIMING_ROOT) -f $(TIMING_ROOT)/timing.mk caravel-timing-fast -j3
+	@$(MAKE) -C $(TIMING_ROOT) -f $(TIMING_ROOT)/timing.mk caravel-timing-slow -j3
+	@find $(PROJECT_ROOT)/signoff/caravel/openlane-signoff -name "*-summary.rpt" \
+		| xargs -I {} tail -n1 "{}"
 	@echo "You can find results for all corners in $(CUP_ROOT)/signoff/caravel/openlane-signoff/timing/"