* Update documentation and CI configurations to work around OpenBLAS OpenMP thrashing issue.
* Update out-of-date link.
* Clarify the situation on Ubuntu and Debian.
* Clarify about pthread compilation.
* Add a bit about the OpenMP variant.
* Make the verbiage consistent everywhere.
* Try to see if the fix works on macOS too.
* Homebrew packages OpenBLAS 0.3.28, so no workaround is needed.
Ryan Curtin
43e6363b85