What is the equivalent of the linux system call clone() on FreeBSD?

Linux has the clone() function that allows the caller more control over 
process cloning than the fork(2) function does.

FreeBSD only has clone() in its Linux emulator code for Linux apps, but 
it seems to be missing in the system.

Is there a library that implements functionality similar to Linux's clone()?

Otherwise, how can clone() calls like this 
https://github.com/cea-hpc/wi4mpi/blob/master/src/common/helper.c#L82 be 
resolved on FreeBSD?


Thanks,

Yuri