Controlling python when building www/chromium

When trying to build www/chromium on a 1 GB Pi3 the system
gets bogged down by five  instances of python2.7 running
simultaneously. This happens using both poudriere and make.

It wasn't a problem a year ago, so presumably something has
changed in chromium's internal build machinery. I've searched
https://www.chromium.org/developers/how-tos/get-the-code and
https://groups.google.com/a/chromium.org/g/chromium-dev
but couldn't find any references to python when compiling, only
when running the browser.  

Is there some way to control how many pythons are loosed at one time?
Most likely two could be accomodated, possibly three. On an 8 GB
Pi4 the five pythons coexist happily, so the behavior is probably
not considered a bug.  

Thanks for reading,

bob prohaska