lang/ruby{27,30,31,32}: Improve qsort_r() detection.

[delphij]

Summary

This change merges the following upstream pull request into the Ruby
interpreter:

https://github.com/ruby/ruby/pull/6332

Adding this patch is no-op right now because we are not using POSIX (GNU)
qsort_r(3) interface yet. It will fix build when the change is applied.

[sunpoet]

I guess we do not need to bump PORTREVISION here since it is no-op now.
Please add either https://github.com/ruby/ruby/pull/6332 or https://github.com/ruby/ruby/commit/7400628cb054a9a9651d69411a100fc9d518099f to your commit message.
Thanks!

[bapt]

no the bump of the port revision is not necessary