sage.env._get_shared_lib_filename: Fix for MULTIARCH

[tobiasdiez]

On distributions that use the multiarch installation scheme, python provides the MULTIARCH sysconfig variable.

We modify sage.env._get_shared_lib_filename to use it.
(Currently it tries to use MULTILIB which does not exist.)
Moreover, I took the opportunity to refactor the code in the _get_shared_lib_filename method to use pathlib.

(extracted from #30371)

CC: @tobiasdiez @kiwifb @tobihan @embray @dimpase

Component: build

Keywords: sd111

Author: Tobias Diez

Branch/Commit: fa4556a

Reviewer: Matthias Koeppe

Issue created by migration from https://trac.sagemath.org/ticket/30901

[sagetrac-git]

Branch pushed to git repo; I updated commit sha1. New commits:

6dd6e5c

Fix compilation

[sagetrac-git]

Changed commit from 94e20c7 to 6dd6e5c

[sagetrac-git]

Branch pushed to git repo; I updated commit sha1. New commits:

eceefb3	Remove string wrap
d345bff	Fix test

[sagetrac-git]

Changed commit from 6dd6e5c to d345bff

[mkoeppe]

comment:4

Why does it change the code for Cygwin? Beyond the scope of the ticket.

And why does it change the doctest to pattern = "*/lib*Singular-*.so"? My guess is that this is untested.

[tobiasdiez]

comment:6

Thanks for the review!

I had to change the Cygwin code as it previously took the last match of search_directories, but on the other OS it was the first match. Thus, in order to unify the code I had to change the order. Please view this as part of "Moreover, I took the opportunity to refactor the code in the _get_shared_lib_filename method to use pathlib.".

For the doctest change, the method returns the following path on my system: /usr/lib/x86_64-linux-gnu/libsingular-Singular-4.1.1.so. This is because of the resolve() statement, which follows symlinks. I had to add resolve() since otherwise the singular library doesn't initialize correctly.

[sagetrac-git]

Branch pushed to git repo; I updated commit sha1. New commits:

c47c4bf

Correct indent

[sagetrac-git]

Changed commit from d345bff to c47c4bf