Emscripten makefile

Question

I am trying to create emscripten logic in Makefile . I am calling cmake command of a CMakeLists.txt. So the logic looks like this

ifeq(EXECUTOR, Emscripten)
    emcmake cmake cmake/CMakeLists.txt
else
   cmake cmake/CMakeLists.txt
endif

And in CMakeLists.txt I have

if(${CMAKE_SYSTEM_NAME} STREQUAL "Emscripten)
    // Do some logic
endif()

So it is crucial to detect this ifeq(EXECUTOR, Emscripten) How can I do that?