flang-20 port is building VERY SLOWLY, "memory pressure" (Activity monitor) is very high

[Joshua Root]

> Building flang has always been CPU+RAM intensive, but it looks like it is
> thrashing now.
>
>    Is there a way to make it go single threaded?  I have like ten "stuck"
> clang processes...

A better solution would be to set build.mem_per_job to something higher 
in the port. It defaults to 1024 (MB) and is used to limit the number of 
parallel build processes based on the available memory.

- Josh