make error when run without access to `/proc`

• Node Version: node = v20.16.0, npm = 10.8.1
• Platform: Linux 6.8.0-40-generic x86_64
• Module: re2

npm error gyp info spawn args [ 'BUILDTYPE=Release', '-C', 'build', '--jobs', 0 ]
npm error make: the '-j' option requires a positive integer argument

When building a package using the systemd security option ProcSubset=pid, gyp sets the number of jobs to 0, which make does not accept.

I believe the relevant code is here: https://github.com/nodejs/node-gyp/blob/e6f4ede10cca28e9edeaa85d7830914c5d1499c7/lib/build.js#L176-L179

The documentation for Node function os.cpus() says:

Returns an array of objects containing information about each logical CPU core. The array will be empty if no CPU information is available, such as if the /proc file system is unavailable.

This can be shown by getting the number of CPUs in a transient service unit:

$ node -e "console.log(require('node:os').cpus().length)"
16

$ sudo systemd-run -p ProcSubset=pid -t -- \
  node -e "console.log(require('node:os').cpus().length)"
0

In the event of os.cpus() not returning any information, I suggest that gyp should either default to some constant number of parallel jobs or let make run as many jobs as it wants.

Start with lib/build.js at lines 176-179 and reproduce the zero-CPU result using the provided systemd-run command with ProcSubset=pid. Check the resulting make arguments and verify that a build no longer passes a zero job count when os.cpus() returns an empty array.