[CMake] purify targets

[Juan Sanchez]

Hello,

Is it possible to build both purify and non purify targets by changing
CMAKE_CXX_LINK_EXECUTABLE?  Unfortunately the following example purify's
both binaries.

ADD_EXECUTABLE(hello helloworld.cc)
SET (CMAKE_CXX_LINK_EXECUTABLE "purify -cache-dir=/tmp
${CMAKE_CXX_LINK_EXECUTABLE}")
ADD_EXECUTABLE(hello.purify helloworld.cc)

Thanks,

Juan