I successfully built the system.img and userdata.img from the source. Then, I used the following commands to flash my cellphone:
fastboot flash userdata data.img fastboot flash system system.img fastboot flash boot boot.img fastboot reboot
But when the cellphone reboots, it fails to come to the desktop, and also fails to connect to my Ubuntu 11.10 in the fastboot mode. My cellphone also seems to come to fastboot mode, because it can stop at my cellphone manufactor's logo, as it did beforehand. But if I connect it to my PC, and I use the fastboot devices, it prompts nothing and seems to be looping in the terminal.