Docker: Update build image with final OCIOv2, Qt 5.15.2, OTIO, Crashpad (#1489)

* Add missing xcb-util-* packages. Qt's libqxcb.so seems to require them in the newer Qt version

* Adjust breakpad install prefix to match CMake change

* Add build script for Olive for quick testing

* .n in CI image actually stands for image revision

* skipping the CI is now supported natively by GitHub Actions

docker/scripts/build_olive.sh

@@ -0,0 +1,17 @@
+#!/usr/bin/env bash
+
+git clone --depth 1 https://github.com/olive-editor/olive.git
+cd olive
+mkdir build
+cd build
+cmake .. -G "Ninja"
+cmake --build .
+
+cmake --install app --prefix appdir/usr
+
+/usr/local/linuxdeployqt-x86_64.AppImage \
+  appdir/usr/share/applications/org.olivevideoeditor.Olive.desktop \
+  -appimage \
+  --appimage-extract-and-run
+
+./Olive*.AppImage --appimage-extract-and-run --version