python3-pyyaml: add PACKAGECONFIG for libyaml

python3-pyyaml: add PACKAGECONFIG for libyaml

For some time now, we have probably been susceptible to host contamination
or at least non-deterministic behavior when libyaml was available in the
build environment.

The symptom is:
ERROR: python3-pyyaml-6.0-r0 do_package_qa: QA Issue:
/usr/lib/python3.11/site-packages/yaml/_yaml.cpython-311-aarch64-linux-gnu.so
contained in package python3-pyyaml requires libyaml-0.so.2()(64bit), but no
providers found in RDEPENDS:python3-pyyaml? [file-rdeps]

>From the documentation:
"""
By default, the setup.py script checks whether LibYAML is installed and
if so, builds and installs LibYAML bindings. To skip the check and force
installation of LibYAML bindings, use the option --with-libyaml:
python setup.py --with-libyaml install

To disable the check and skip building and installing LibYAML bindings,
use --without-libyaml:
python setup.py --without-libyaml install
"""

Instead of leaving this to chance, add PACKAGECONFIG and by default build
with the faster libyaml bindings.

Signed-off-by: Tim Orling <tim.orling@konsulko.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>