The version of make which ships with Xcode is old (as Apple has stopped updating GPL software in general, and hopefully new builds of GNU make are GPL3 anyway),

The version of make which ships with Xcode is old (as Apple has stopped updating GPL software in general, and hopefully new builds of GNU make are GPL3 anyway), but it is otherwise not in any way somehow tied to Xcode's toolchain: it is a normal copy of GNU make 3.81 which runs commands the same as any other copy of make (as you provide them, and using the path).