Running out of RAM building devel/llvm13

[Stephen Montgomery-Smith]

Does anyone else have the problem of running out of RAM when building 
devel/llvm13?  I have 6 CPUS, 4G of RAM, and 4G of swap.

I can solve it by building with MAKE_JOBS_UNSAFE=yes, but then the build 
is so slow.

It seems that there is a small part of the build which requires a lot of 
RAM, and it would be nice to restrict just that portion of the build to 
just one CPU.

Thanks, Stephen