Arduino on Xcode Project — Official Thread

Hi,
I found I can't build "Marlin" in embedXcode, while in Arduino IDE, it works well. The error code is here

7.2-LINK: .elf < . 	mega2560	Builds/	.
/Applications/Arduino.app/Contents/Resources/Java/hardware/tools/avr/bin/avr-gcc -mmcu=atmega2560 -lm -Wl,--gc-sections -Os  -o Builds/embeddedcomputing.elf Builds/LocalLibrary.o Builds/main.o Builds/embeddedcomputing.a -lc
Builds/embeddedcomputing.a(MarlinSerial.o): In function `__vector_25':
/Users/my/Documents/Arduino/libraries/Marlin/MarlinSerial.cpp:54: multiple definition of `__vector_25'
Builds/embeddedcomputing.a(HardwareSerial.o):/Applications/Arduino.app/Contents/Resources/Java/hardware/arduino/cores/Arduino/HardwareSerial.cpp:118: first defined here
Builds/embeddedcomputing.a(MarlinSerial.o):(.bss.rx_buffer+0x0): multiple definition of `rx_buffer'
Builds/embeddedcomputing.a(HardwareSerial.o):/Applications/Arduino.app/Contents/Resources/Java/hardware/arduino/cores/Arduino/HardwareSerial.cpp:113: first defined here
/Applications/Arduino.app/Contents/Resources/Java/hardware/tools/avr/bin/../lib/gcc/avr/4.3.2/../../../../avr/bin/ld: Warning: size of symbol `rx_buffer' changed from 68 in Builds/embeddedcomputing.a(HardwareSerial.o) to 132 in Builds/embeddedcomputing.a(MarlinSerial.o)
make: *** [Builds/embeddedcomputing.elf] Error 1

Marlin rewrites the serial library, which is conflict to HardwareSerial. It's really odd why Arduino can compile it...
How can I deal with it?