Run parallel jobs, allocate cpu cores per job and allocate memory per job
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Fromager provides `cpu_cores_per_job` and `memory_per_job_gb` options which are
related to build systems and can be used as a per package setting when multiple
cores and significant amount of memory is available on a build system. On the
other hand, the `--jobs` overrides the default calculations based on the other
settings. For example, when you pass `--jobs 4` then at most 4 processes will
run in parallel when building a given wheel. By default, fromager computes a
number of jobs and that value can be influenced based on the per-package
settings. Note that the jobs are all within the context of building a single
wheel.

The `--jobs` option of fromager allows to set the maximum number of wheel build
jobs to run in parallel. Below is an example which uses the `--jobs` option
along with the bootstrap command

.. code-block:: bash

   fromager --jobs 4 bootstrap torch

For this example, the maximum number of jobs fromager will run in parallel is 4.

The `cpu_cores_per_job` is a package setting that allows to scale parallel jobs
by available CPU cores. The default value is set to 1 which indicates as many
parallel jobs as CPU logical cores. Example: `cpu_cores_per_job = 2` indicates
allocating 2 cores per job. This setting should always have value greater than or
equal to 1

The `memory_per_job_gb` is a package setting that allows to scale parallel jobs
by available virtual memory without swap. The default value is set to 1.0 which
indicates that each parallel job requires 1 GB virtual memory Example:
`memory_per_job_gb = 0.5` indicates that each parallel job requires 512 MB
virtual memory This setting should always have value greater than or equal to
0.1