Enable parallelization while compiling Sage's documentation

Problem Description

On a 40-code system I compile sage by running MAKE="make -j40" make -j40. Make does quite a decent job in parallelizing compilation of Sage's code sources, but when it comes to compiling Sage's documentation the process mainly goes in a single thread. As a result, compiling Sage's documentation takes significantly long time (maybe even longer than the rest of Sage).

Proposed Solution

I hope it's possible to enable parallelization in compilation of Sage's documentation, although I do not have a particular recipe. This should dramatically speed up the overall compilation of Sage from sources.

Alternatives Considered

N/A

Additional Information

No response

Is there an existing issue for this?

[X] I have searched the existing issues for a bug report that matches the one I want to file, without success.

sagemath / sage