feat(qt5): add qt5serialport and qt5serialbus packages

[titobrasolin]

These packages enable serial communication functionalities for Qt5 applications on OpenWrt targets.

[titobrasolin]

CI Failure: Qt5 Source URLs (Ref: #101)

Hi! I noticed the build tests failed. This is a known infrastructure issue caused by the Qt5 source URLs being moved to the official archives, as I documented in detail in issue #101 (which I opened with my corporate account @titobrasolin-ke).

As shown in the logs, curl returns a 404 because the CI is still attempting to fetch submodules from /official_releases/ instead of /archive/:

curl: (22) The requested URL returned error: 404 Not Found
https://download.qt.io/official_releases/qt/5.15/5.15.16/submodules/...

This failure is unrelated to the logic of my changes. This PR has already successfully passed the initial metadata and formatting checks (Signed-off-by, commit comments, etc.).

I am available to rebase this PR or re-run the actions as soon as the fix for the Qt5 base URL (proposed in #101) is merged. Thanks!

[titobrasolin]

PR #72 is currently on [skip ci] to avoid noise. It will be ready for full CI once the URL fix in #102 is merged.

[titobrasolin]

The build failed during the Meson configuration phase despite the logs showing a successful installation of the Python dependencies at the beginning of the process.

Related Issue: mesa fails to build due to yaml module not being found · Issue #61 · openwrt/video

Failure Analysis:

The error Python (3.x) mako module >= 0.8.0 required suggests a path mismatch or environment isolation issue:

• Inconsistency: The logs confirm Mako-1.3.5 was successfully built and installed using /builder/staging_dir/hostpkg/bin/pip3.14. However, Meson (running under Python 3.14.3) fails to locate it during the setup phase.
• Apparent Path Correctness: Both the pip3.14 install command and the subsequent meson.py setup (which includes the specific PYTHONPATH) seem to point to the same hostpkg staging directory.
• Potential Cause: Despite the consistent paths, pip might have installed the wheels in a location not covered by the defined PYTHONPATH (e.g., if a --target or --prefix flag was missing in the host-build environment), or there is an issue with how Python 3.14.x handles the site-packages in this specific buildroot.

Relevant logs:

1. Python Dependencies Installation:
2026-03-30T23:45:53.2744899Z ... /builder/staging_dir/hostpkg/bin/pip3.14 install --no-binary :all: --progress-bar off --require-hashes --requirement ./host-pip-requirements.txt
...
2026-03-30T23:47:24.4631062Z Successfully built Mako MarkupSafe ply pycparser PyYAML
2026-03-30T23:47:24.7702673Z Successfully installed Mako-1.3.5 MarkupSafe-2.1.5 PyYAML-6.0.2 ply-3.11 pycparser-2.21

2. Meson Setup with matching PYTHONPATH:
2026-03-30T23:47:24.9317077Z PYTHONPATH="/builder/staging_dir/hostpkg/lib/python3.14:/builder/staging_dir/hostpkg/lib/python3.14/site-packages" /builder/staging_dir/hostpkg/bin/python3 /builder/staging_dir/host/bin/meson.py setup --native-file /builder/build_dir/hostpkg/mesa-25.2.4/openwrt-native.txt ...
...
2026-03-30T23:47:26.6357885Z Program python found: YES 3.14.3
2026-03-30T23:47:26.6358466Z .../mesa-25.2.4/meson.build:933:2: ERROR: Problem encountered: Python (3.x) mako module >= 0.8.0 required to build mesa.

It seems the host-python environment is being strictly isolated, or the installed modules are not being placed where the subsequent build steps expect them to be.