Trac #30803: Upgrade pybind11 to 2.6.0 to fix "critical incompatibili…

…ty with Python 3.9.0"

(from #30184)

From https://pybind11.readthedocs.io/en/latest/

{{{
Warning

Combining older versions of pybind11 (< 2.6.0) with the brand-new Python
3.9.0 will trigger undefined behavior that typically manifests as
crashes during interpreter shutdown (but could also destroy your data.
You have been warned.)

We recommend that you wait for Python 3.9.1 slated for release in
December, which will include a fix that resolves this problem. In the
meantime, please update to the latest version of pybind11 (2.6.0 or
newer), which includes a temporary workaround specifically when Python
3.9.0 is detected at runtime.
}}}

https://pypi.org/project/pybind11/#history

`pybind11` is a dependency of `scipy`.

URL: https://trac.sagemath.org/30803
Reported by: mkoeppe
Ticket author(s): Matthias Koeppe
Reviewer(s): Dima Pasechnik

build/pkgs/pybind11/checksums.ini

@@ -1,5 +1,5 @@
 tarball=pybind11-VERSION.tar.gz
-sha1=21cdff0a455438b9727acf2b6f125fa54434eea8
-md5=5355e1fd05c8eedef19cc9bfd3d82a77
-cksum=726764164
+sha1=08c988c8230261ce8c8d9242af71af2ef6f69338
+md5=1cc822c9a6716c44be8b86a9082816f7
+cksum=1801766832
 upstream_url=https://pypi.io/packages/source/p/pybind11/pybind11-VERSION.tar.gz

build/pkgs/pybind11/package-version.txt

@@ -1 +1 @@
-2.5.0
+2.6.0