build: httpd: also declutter sourcecode

httpd/Makefile

@@ -3,21 +3,26 @@ CC_FLAGS = -mmcs51 -I. -I../uip
 ASM = sdas8051
 AFLAGS= -plosgff
 
+BUILDDIR = output/
+
 SRCS = httpd.c page_impl.c
-OBJS = ${SRCS:.c=.rel}
+OBJS = ${SRCS:%.c=$(BUILDDIR)%.rel}
 
-all: $(OBJS)
+all: create_build_dir $(OBJS)
 
-%.asm: %.c
-	$(CC) $(CC_FLAGS) -c -S $<
+create_build_dir:
+	mkdir -p $(BUILDDIR)
 
-%.rel: %.asm
+$(BUILDDIR)%.asm: %.c
+	$(CC) $(CC_FLAGS) -o $@ -c -S $<
+
+$(BUILDDIR)%.rel: $(BUILDDIR)%.asm
 	./treatasm.py $^ >$^.new
 	mv $^.new $^
-	${ASM} ${AFLAGS} $^
+	${ASM} ${AFLAGS} -o $@ $^
 
 clean:
-	rm .asm *.lst *.rel *.rst *.sym
+	rm -r $(BUILDDIR)
 
 .PHONY: all clean