[CMake] ExternalProject_Add and BUILD_COMMAND

[Francisco Requena Espí]

I want to use ExternalProject_Add, but in order to build my project I
need to call 'make macosx'. I do:

EXTERNALPROJECT_ADD(PROJ SOURCE_DIR
"${CMAKE_CURRENT_SOURCE_DIR}/proj1" CONFIGURE_COMMAND "" BUILD_COMMAND
"make macosx" BUILD_IN_SOURCE 1 INSTALL_COMMAND "")

But it doesn't work (it says it cannot find command make macosx). If I
do "make" it works, but I need to give an argument to it. How I do
pass an argument? It's needed something like BUILD_COMMAND_ARGS
"macosx"?

Thanks.