[Someone]

I would think a process launched by make can easily obtain the process ID of its parent process. If so, no heuristics are needed to find the correct instance of make.

On the other hand, reading the command line isn't sufficient. The -j argument does not require a job count, defaulting to "as many as possible".

Also, you would have to check your OS, too since the -j argument is ignored on MS-DOS (https://www.gnu.org/software/make/manual/make.html#Options-S...)