[CMake] CMake CVS DEFINE_SYMBOL only works once

[Brandon J. Van Every]

I've built CMake from CVS using MinGW / MSYS.  If I write code like the 
following:

SET_TARGET_PROPERTIES(${CHICKEN_UNSAFE_LIB_NAME} PROPERTIES
  DEFINE_SYMBOL C_BUILDING_LIBCHICKEN)
SET_TARGET_PROPERTIES(${CHICKEN_UNSAFE_LIB_NAME} PROPERTIES
  DEFINE_SYMBOL C_UNSAFE_RUNTIME)

only the last symbol will be defined, i.e. -DC_UNSAFE_RUNTIME.  This I 
determine by inspecting the output of "make -n".


Cheers,
Brandon Van Every