cd: add DEB, RPM and Arch Linux packages

- Add CPack configuration in CMakeLists.txt for .deb and .rpm generation
  with declared runtime dependencies.
- Add Arch Linux PKGBUILD template under app/packaging/arch/ and build it
  inside the official archlinux:base-devel Docker container.
- Extend CD workflow with deb, rpm and archlinux jobs and attach the
  resulting packages to the draft release.

app/packaging/arch/PKGBUILD.in

@@ -0,0 +1,27 @@
+# Maintainer: Oak Video Editor Team
+pkgname=oak-video-editor
+pkgver=@VERSION@
+pkgrel=1
+pkgdesc="Oak - Non-linear video editor"
+arch=('x86_64')
+url="https://oakvideoeditor.org"
+license=('GPL3')
+depends=('qt6-base' 'qt6-tools' 'ffmpeg' 'openimageio' 'opencolorio' 'openexr' 'expat' 'portaudio' 'mesa' 'vulkan-icd-loader' 'libxkbcommon')
+makedepends=('cmake' 'ninja' 'git' 'pkgconf')
+source=("${pkgname}-${pkgver}.tar.gz")
+md5sums=('SKIP')
+
+build() {
+  cd "${srcdir}/${pkgname}-${pkgver}"
+  cmake -S . -B build -G Ninja \
+    -DCMAKE_BUILD_TYPE=Release \
+    -DCMAKE_INSTALL_PREFIX=/usr \
+    -DBUILD_QT6=ON \
+    -DCMAKE_DISABLE_FIND_PACKAGE_Vulkan=ON
+  cmake --build build
+}
+
+package() {
+  cd "${srcdir}/${pkgname}-${pkgver}"
+  DESTDIR="${pkgdir}" cmake --install build
+}