arch: x86 -> x86_64 and build system changes

arch/x86_64/elfboot/Makefile

@@ -0,0 +1,36 @@
+DEST=$(O)/elfboot
+CFLAGS=-c -Wall -O
+CFLAGS_TEST=-DTEST
+
+all: $(DEST) $(DEST)/elfboot
+
+$(DEST)/elfboot: $(DEST)/elfboot.bin
+	cp $^ $@
+	truncate -s $(shell expr '(' `stat -c '%s' $^` + 4095 ')' / 4096 '*' 4096) $@
+
+$(DEST)/elfboot.bin: $(DEST)/elfboot.elf
+	$(OBJCOPY) -O binary $^ $@
+
+$(DEST)/elfboot.elf: $(DEST)/head.o $(DEST)/elfboot.raw.o raw.lds
+	$(LD) $(LDFLAGS_RAW) -T raw.lds -o $@ $^
+
+$(DEST)/elfboot_test: $(DEST)/elfboot.test.o $(DEST)/test_main.o
+	$(CC) -o $@ $^
+
+$(DEST)/head.o: head.S
+	$(CC) $(CFLAGS) -o $@ $^
+
+$(DEST)/elfboot.raw.o: elfboot.c
+	$(CC) $(CFLAGS) -o $@ $^
+
+$(DEST)/elfboot.test.o: elfboot.c
+	$(CC) $(CFLAGS) $(CFLAGS_TEST) -o $@ $^
+
+clean:
+	$(RM) $(DEST)/elfboot *.bin $(DEST)/*.elf $(DEST)/elfboot_test *.o
+
+disas:
+	$(OBJDUMP) -b binary -m i386:x86-64 -D $(DEST)/elfboot.bin
+
+$(DEST):
+	@mkdir -p $(DEST)