...

src/runtime/makefile

@@ -1,5 +1,15 @@
-x86_64:
-	gcc -nostdlib -ffreestanding -c platform/x86_64.s runtime.c
+CC = gcc
+CFLAGS = -nostdlib -ffreestanding -Wall -Werror -Wextra
+
+x64: runtime.o x64.o
+	mkdir -p out
+	ar rcs out/libruntime.a runtime.o x64.o
+
+runtime.o: runtime/runtime.c
+	$(CC) $(CFLAGS) -c runtime/runtime.c -o runtime.o
+
+x64.o: runtime.o platform/x64.s
+	$(CC) $(CFLAGS) -c platform/x64.s -o x64.o
 
 clean:
-	rm runtime.o
+	rm -r out runtime.o x64.o