Add setup build environment action

.gitea/actions/setup-build-env/README.md

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+# setup-build-env Gitea Action
+
+Reusable Gitea/GitHub-compatible composite action for Debian/Ubuntu runners. It installs:
+
+- Clang/LLVM, default `22`
+- Meson, installed in an isolated Python virtual environment to avoid PEP 668 `externally-managed-environment` errors
+- Ninja
+- Python 3, pip, venv
+- Vulkan development tooling / SDK packages
+
+## Local use inside a repository
+
+Put this directory at:
+
+```text
+.gitea/actions/setup-build-env
+```
+
+Then use it from a workflow:
+
+```yaml
+name: build
+
+on:
+  push:
+  pull_request:
+
+jobs:
+  linux:
+    runs-on: ubuntu-latest
+    container:
+      image: debian:trixie
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: ./.gitea/actions/setup-build-env
+        with:
+          llvm-version: "22"
+          vulkan-source: apt
+
+      - run: |
+          meson setup build --native-file build_options/meson-clang-linux
+          meson compile -C build
+```
+
+## Use from a shared action repository
+
+Create a dedicated repository, for example:
+
+```text
+gitea.example.com/actions/setup-build-env
+```
+
+Put `action.yml`, `scripts/setup.sh`, and this README at the root of that repository. Then tag it:
+
+```bash
+git tag v1
+git push origin v1
+```
+
+Use it from all projects:
+
+```yaml
+- uses: actions/setup-build-env@v1
+```
+
+or with your full Gitea owner/repo path, depending on your Gitea Actions configuration:
+
+```yaml
+- uses: your-org/setup-build-env@v1
+```
+
+## Inputs
+
+| Input | Default | Description |
+| --- | --- | --- |
+| `llvm-version` | `22` | LLVM/Clang major version. Installs packages like `clang-22`, `lld-22`, `llvm-22-dev`. |
+| `meson-version` | `latest` | Meson version installed into `/opt/meson-venv`. Use e.g. `1.6.1` to pin. |
+| `install-vulkan` | `true` | Install Vulkan packages. |
+| `vulkan-source` | `apt` | `apt` for distro packages, or `lunarg` for the LunarG apt repository. |
+| `lunarg-sdk-version` | `1.4.309.0` | LunarG SDK version used when `vulkan-source: lunarg`. |
+| `make-default` | `true` | Makes `clang`, `clang++`, `lld`, etc point at the selected LLVM version through `update-alternatives`. |
+
+## Notes
+
+- This action assumes an apt-based Debian/Ubuntu runner/container.
+- If your runner is not root, it needs passwordless `sudo`.
+- `vulkan-source: apt` is recommended for CI because it is the most robust across Debian/Ubuntu images.
+- `vulkan-source: lunarg` is best used on Ubuntu images supported by LunarG.
+- Because this installs system packages, caching the entire result is normally done at the runner/container-image level. For faster builds, consider creating your own Docker image from the commands in `scripts/setup.sh`.

.gitea/actions/setup-build-env/action.yml

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+name: Setup C/C++ Vulkan build environment
+description: Install Clang/LLVM, Meson, Ninja, Python, and Vulkan SDK packages on Debian/Ubuntu Gitea runners.
+
+inputs:
+  llvm-version:
+    description: LLVM/Clang major version to install.
+    required: false
+    default: "22"
+  meson-version:
+    description: Meson version to install via isolated Python venv. Use "latest" for newest.
+    required: false
+    default: "latest"
+  install-vulkan:
+    description: Install Vulkan SDK/development packages.
+    required: false
+    default: "true"
+  vulkan-source:
+    description: "Vulkan package source: apt or lunarg. apt is more robust on self-hosted runners."
+    required: false
+    default: "apt"
+  lunarg-sdk-version:
+    description: LunarG SDK version, used only when vulkan-source=lunarg. Example: 1.4.309.0
+    required: false
+    default: "1.4.309.0"
+  make-default:
+    description: Make selected clang/clang++/llvm tools the default compiler commands.
+    required: false
+    default: "true"
+
+runs:
+  using: composite
+  steps:
+    - name: Install build environment
+      shell: bash
+      run: |
+        "${{ github.action_path }}/scripts/setup.sh"
+      env:
+        LLVM_VERSION: ${{ inputs.llvm-version }}
+        MESON_VERSION: ${{ inputs.meson-version }}
+        INSTALL_VULKAN: ${{ inputs.install-vulkan }}
+        VULKAN_SOURCE: ${{ inputs.vulkan-source }}
+        LUNARG_SDK_VERSION: ${{ inputs.lunarg-sdk-version }}
+        MAKE_DEFAULT: ${{ inputs.make-default }}

.gitea/actions/setup-build-env/scripts/setup.sh

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+#!/usr/bin/env bash
+set -euo pipefail
+
+LLVM_VERSION="${LLVM_VERSION:-22}"
+MESON_VERSION="${MESON_VERSION:-latest}"
+INSTALL_VULKAN="${INSTALL_VULKAN:-true}"
+VULKAN_SOURCE="${VULKAN_SOURCE:-apt}"
+LUNARG_SDK_VERSION="${LUNARG_SDK_VERSION:-1.4.309.0}"
+MAKE_DEFAULT="${MAKE_DEFAULT:-true}"
+
+log() { printf '\n\033[1;34m==> %s\033[0m\n' "$*"; }
+warn() { printf '\n\033[1;33mwarning: %s\033[0m\n' "$*" >&2; }
+
+if command -v sudo >/dev/null 2>&1 && [ "$(id -u)" -ne 0 ]; then
+  SUDO=sudo
+else
+  SUDO=""
+fi
+
+export DEBIAN_FRONTEND=noninteractive
+
+apt_install() {
+  $SUDO apt-get install -y --no-install-recommends "$@"
+}
+
+log "Installing base packages"
+$SUDO apt-get update
+apt_install \
+  ca-certificates \
+  curl \
+  gnupg \
+  lsb-release \
+  software-properties-common \
+  wget \
+  xz-utils \
+  build-essential \
+  pkg-config \
+  git \
+  python3 \
+  python3-venv \
+  python3-pip \
+  ninja-build
+
+log "Installing LLVM/Clang ${LLVM_VERSION}"
+if ! apt-cache show "clang-${LLVM_VERSION}" >/dev/null 2>&1; then
+  warn "clang-${LLVM_VERSION} is not in the current apt sources; adding apt.llvm.org"
+  curl -fsSL https://apt.llvm.org/llvm-snapshot.gpg.key | $SUDO gpg --dearmor -o /usr/share/keyrings/llvm-snapshot.gpg
+  CODENAME="$(. /etc/os-release && printf '%s' "${VERSION_CODENAME:-}")"
+  if [ -z "$CODENAME" ]; then
+    CODENAME="$(lsb_release -sc)"
+  fi
+  echo "deb [signed-by=/usr/share/keyrings/llvm-snapshot.gpg] http://apt.llvm.org/${CODENAME}/ llvm-toolchain-${CODENAME}-${LLVM_VERSION} main" | \
+    $SUDO tee "/etc/apt/sources.list.d/llvm-${LLVM_VERSION}.list" >/dev/null
+  $SUDO apt-get update
+fi
+
+apt_install \
+  "clang-${LLVM_VERSION}" \
+  "clang-tools-${LLVM_VERSION}" \
+  "lld-${LLVM_VERSION}" \
+  "lldb-${LLVM_VERSION}" \
+  "llvm-${LLVM_VERSION}" \
+  "llvm-${LLVM_VERSION}-dev"
+
+if [ "$MAKE_DEFAULT" = "true" ]; then
+  log "Making Clang ${LLVM_VERSION} the default compiler for this runner"
+  for tool in clang clang++ clang-cpp llvm-ar llvm-ranlib llvm-nm llvm-strip lld lldb; do
+    if command -v "${tool}-${LLVM_VERSION}" >/dev/null 2>&1; then
+      $SUDO update-alternatives --install "/usr/bin/${tool}" "${tool}" "$(command -v "${tool}-${LLVM_VERSION}")" 100
+    fi
+  done
+fi
+
+log "Installing Meson in an isolated venv"
+MESON_VENV="/opt/meson-venv"
+$SUDO python3 -m venv "$MESON_VENV"
+$SUDO "$MESON_VENV/bin/python" -m pip install --upgrade pip setuptools wheel
+if [ "$MESON_VERSION" = "latest" ]; then
+  $SUDO "$MESON_VENV/bin/python" -m pip install --upgrade meson
+else
+  $SUDO "$MESON_VENV/bin/python" -m pip install --upgrade "meson==${MESON_VERSION}"
+fi
+$SUDO ln -sf "$MESON_VENV/bin/meson" /usr/local/bin/meson
+
+if [ "$INSTALL_VULKAN" = "true" ]; then
+  case "$VULKAN_SOURCE" in
+    apt)
+      log "Installing Vulkan development packages from distro apt repositories"
+      apt_install \
+        libvulkan-dev \
+        vulkan-tools \
+        vulkan-validationlayers \
+        glslang-tools \
+        spirv-tools \
+        spirv-headers || {
+          warn "Some Vulkan packages were unavailable; retrying minimal Vulkan package set"
+          apt_install libvulkan-dev vulkan-tools glslang-tools spirv-tools
+        }
+      ;;
+    lunarg)
+      log "Installing Vulkan SDK from LunarG (${LUNARG_SDK_VERSION})"
+      . /etc/os-release
+      if [ "${ID:-}" != "ubuntu" ]; then
+        warn "LunarG apt repo is Ubuntu-oriented. Falling back to distro apt Vulkan packages."
+        apt_install libvulkan-dev vulkan-tools glslang-tools spirv-tools
+      else
+        CODENAME="${VERSION_CODENAME:-$(lsb_release -sc)}"
+        curl -fsSL https://packages.lunarg.com/lunarg-signing-key-pub.asc | \
+          $SUDO gpg --dearmor -o /usr/share/keyrings/lunarg.gpg
+        echo "deb [signed-by=/usr/share/keyrings/lunarg.gpg] https://packages.lunarg.com/vulkan/${LUNARG_SDK_VERSION}/ubuntu ${CODENAME} main" | \
+          $SUDO tee /etc/apt/sources.list.d/lunarg-vulkan-sdk.list >/dev/null
+        $SUDO apt-get update
+        apt_install vulkan-sdk
+      fi
+      ;;
+    *)
+      echo "Unsupported VULKAN_SOURCE=${VULKAN_SOURCE}; expected apt or lunarg" >&2
+      exit 2
+      ;;
+  esac
+fi
+
+log "Versions"
+python3 --version
+python3 -m pip --version || true
+meson --version
+ninja --version
+clang --version
+if command -v vulkaninfo >/dev/null 2>&1; then
+  vulkaninfo --summary || true
+fi
+
+log "Build environment ready"