If you want to write a portable makefile, you use a CP variable which is conditionally set depending on what uname says, e.g. cp -r on GNU Linux and whatever it

If you want to write a portable makefile, you use a CP variable which is conditionally set depending on what uname says, e.g. cp -r on GNU Linux and whatever it is on Mac OS. But also, copying files around is a bit out of make's scope, as it is a tool for transforming files. Most standard tools that are used in makefiles (sed, awk, m4, c toolchain) have posix interfaces, and other compilers usually don't have incompatible competing implementations. Even if you want to use a certain implementations features, say GNU features of awk, gawk+GNU coreutils are available for all popular systems, as well as bsdutils. Requiring them is better than when every program require its own build system because they are portable and reusable packages.