http://blog.youkuaiyun.com/wulin250/archive/2009/07/24/4377019.aspx
Example:
SMDK6410.bat: set BSP_EPSON_S1R72V27=1
oallib/sources: !IF "$(BSP_EPSON_S1R72V27)" == "1"
CDEFINES=$(CDEFINES) -DEPSON_USB
!ENDIF
init.c: #ifdef EPSON_USB
InitializeSromBank();
#endif