[RFC] xbps-src: default XBPS_MAKEJOBS to nproc

[classabbyamp]

previously this defaulted to 1. In some rare cases, nproc is not desirable, but that can be easily overriden in the standard ways, etc/conf or -jN.

For compatibility with other distros, it defaults to 1 when nproc is not available.

Testing the changes

• I tested the changes in this PR: YES

[abenson]

I kind of support this. I just wonder what the default should be; all cores, some cores, or specified cores.

[dataCobra]

Could we use the amount of cores divided by two?

I support this also, but I feel like defaulting to all cores is a bit too much?

[jcgruenhage]

I think nproc would be a good default. I usually run with -j 16 on my laptop, and it's rarely a problem. The only times when I run into trouble is not due to CPU load either, but because I'm exhausting memory (which has been solved by going 16->64gig) or exhausting disk space.

[ahesford]

I've seen plenty of historical recommendation for spawning twice as many jobs as CPUs with make, so defaulting to nproc seems reasonable. People with SMT CPUs will have the "right" value, and those without get a reduced "compromise" value.

[dataCobra]

Most of the time I'm building stuff while doing other things on my machines. As I mentioned above I still feel like defaulting to all cores is a bit too much.

On some of my machines multi tasking would no longer be possible.

[ahesford]

Compilation is I/O bound, which is why the usual recommendation is to use twice as many processes as you have CPUs. There's no need to try to get clever setting this. You can always override the parallelism if you find it too intensive, just as you have to override it now to get any parallelism.

[vincele]

Was wondering the other day why this defaults to no parallelism (void newbie here).
LGTM