lang/python314: limit compileall to MAKE_JOBS_NUMBER

This seems to help with cross-builds (qemu) for RISC-V machines.

Obtained from: Siva Mahadevan
Differential Revision: https://reviews.freebsd.org/D55050

(cherry picked from commit c1d4c7da048b60be5d2d2c5ef47653ac34c3bb35)