package/libselinux: allow pip to use system-provided packages

package/libselinux: allow pip to use system-provided packages

Since the bump of pip to version 25.3 in commit
285097051d4a7dd821f01d15c705867f7e26c635, the build of the Python
bindings of libselinux is broken for both the host and target
variants.

For the host variant, because "pip install" no longer finds the
system-provided setuptools and tries to download setuptools by itself,
causing build issues because our host-python doesn't have SSL support:

  Could not fetch URL https://pypi.org/simple/setuptools/: There was a problem confirming the ssl certificate: HTTPSConnectionPool(host='pypi.org', port=443): Max retries exceeded with url: /simple/setuptools/ (Caused by SSLError("Can't connect to HTTPS URL because the SSL module is not available.")) - skipping

For the target variant, because "pip install" no longer finds the
sysconfigdata package:

  ModuleNotFoundError: No module named '_sysconfigdata__linux_sparc64-linux-gnu'
  [end of output]

We fix this by taking a patch from Debian, which is slightly tweaked
to also cover our host package (the original Debian patch was passing
--no-build-isolation only when DESTDIR was not empty, but in Buildroot
host packages are built with DESTDIR empty, and we do need
--no-build-isolation).

Fixes:

  https://autobuild.buildroot.net/results/0e9de0c0d8b6ec57eea9f8834f02076b296ba4f1/ (host-libselinux)
  https://autobuild.buildroot.org/results/1b87c659f1901b0bf33fa4a2ff0ed40b13114bba/ (libselinux)

Signed-off-by: Bernd Kuhls <bernd@kuhls.net>
Co-Authored-By: Julien Olivain <ju.o@free.fr>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>