Compiling BASIC256 on Raspberry Pi / Linux ARM64

Requires Qt6 (minimum Qt 6.2; CI builds against whatever Qt6 Debian Trixie
currently ships, e.g. 6.8.x). 

The authoritative, continuously-tested steps are
.github/scripts/build_Linux_RPi_Trixie.sh (build) and
.github/scripts/package_Linux_RPi_Trixie.sh /
package_Linux_RPi_AppImage.sh (packaging) -- if these instructions and those
scripts ever disagree, trust the scripts.

Tested on: Debian 13 "Trixie", native aarch64 (e.g. Raspberry Pi 4/5).

Dependencies:

  sudo apt-get update && sudo apt-get install -y \
    build-essential cmake flex bison \
    flite libflite1 \
    gstreamer1.0-plugins-base gstreamer1.0-plugins-good gstreamer1.0-plugins-bad gstreamer1.0-alsa \
    gstreamer1.0-libav gstreamer1.0-pipewire pipewire pipewire-pulse \
    libpipewire-0.3-0 libpipewire-0.3-dev libgstreamer1.0-0 libgstreamer-plugins-base1.0-0 \
    libasound2-dev espeak-ng libespeak-ng-dev libspeechd-dev speech-dispatcher \
    qt6-base-dev qt6-base-dev-tools qt6-tools-dev qt6-tools-dev-tools qt6-l10n-tools \
    qt6-multimedia-dev qt6-serialport-dev qt6-speech-dev qt6-declarative-dev \
    libgl1-mesa-dev libx11-dev patchelf

Note: qt6-declarative-dev is required even though this project has no QML
of its own -- Qt6TextToSpeech's own CMake package config depends on
Qt6QmlIntegration, and find_package(Qt6 ... TextToSpeech) fails without it.

Build (native ARM64 compile, Qt6 found automatically from the apt install):

  cmake -B build -DCMAKE_BUILD_TYPE=Release
  cmake --build build --config Release -j$(nproc)

The resulting binary is build/basic256.

Packaging into a standalone, relocatable distribution folder (bundles Qt6 +
GStreamer + speech libraries with patchelf-adjusted rpaths so it runs
without the dev packages installed) is handled by
.github/scripts/package_Linux_RPi_Trixie.sh, and an AppImage variant by
.github/scripts/package_Linux_RPi_AppImage.sh. See those scripts for the
exact library/plugin list.

Audio on Raspberry Pi:
https://www.raspberrypi.org/documentation/configuration/audio-config.md
