Hello Guix,

I noticed building 'python-minimal' that its tests seemed to have poor
memory performance, i.e. using *a lot* of RAM.  I thought maybe
dropping --cores=... would help, but it did not; the tests use all
available cores by default.  The attached patch fixes this issue,
though, the package still uses all cores while building some extension
libraries.

I suppose this patch would go to core-updates?

Cheers,
`~Eric