Clean up each performance test separately

Makefile

@@ -76,7 +76,7 @@ ridiculous_speed_demo: clean $(RIDICULOUS_STATS) #: Compare other techniques
 
 %.timings.txt: code/speed_demo/%/main.exe
 	$(call banner, Sampling performance of $<)
-	(for i in `seq 1 2`; do \
+	(for i in `seq 1 10`; do \
 		time -f "%U" ./$<; \
 	done) 2>&1 | tee $@
 
@@ -121,4 +121,10 @@ enter_container: docker_build.txt #: Run an interactive shell in the container
 	docker run -it -v $(PWD):/workspace ifuncd-up:latest
 
 clean:  #: Remove any build detritus
+	make -C code/speed_demo/always clean
+	make -C code/speed_demo/fixed clean
+	make -C code/speed_demo/ifunc clean
+	make -C code/speed_demo/pointer clean
+	make -C code/speed_demo/struct clean
+	make -C code/speed_demo/upfront clean
 	rm -f *.txt *.exe