...

src/runtime/makefile

@@ -1,15 +1,16 @@
-CC = gcc
+CC ?= x86_64-linux-gnu-gcc
+TARGET ?= x64
+
 CFLAGS = -nostdlib -ffreestanding -Wall -Werror -Wextra
 
-x64: runtime.o x64.o
+libruntime: out-int/runtime.o
+	$(CC) $(CFLAGS) -c targets/$(TARGET).s -o out-int/$(TARGET).o
 	mkdir -p out
-	ar rcs out/libruntime.a runtime.o x64.o
+	ar rcs out/libruntime_$(TARGET).a out-int/runtime.o out-int/$(TARGET).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
+out-int/runtime.o: runtime/runtime.c
+	mkdir -p out-int
+	$(CC) $(CFLAGS) -c runtime/runtime.c -o out-int/runtime.o
 
 clean:
-	rm -r out runtime.o x64.o
+	rm -r out out-int