appimage build: build and include libxcb-util1

fixes #8011

> Upgraded from Appimage 4.1.5 to 4.3.2 on MX-Linux 19.
> The new version fails to start with:
>
> ```
> $ electrum
> qt.qpa.plugin: Could not load the Qt platform plugin "xcb" in "" even though it was found.
> This application failed to start because no Qt platform plugin could be initialized. Reinstalling the application may > fix this problem.
>
> Available platform plugins are: eglfs, linuxfb, minimal, minimalegl, offscreen, vnc, wayland-egl, wayland, wayland-xcomposite-egl, wayland-xcomposite-glx, webgl, xcb.
>
> Aborted (core dumped)
> ```

debian 10 only distributes libxcb-util0.
debian 11 distributes libxcb-util1.
our base image atm is debian 10, so we build the package from source.

Author: SomberNight

contrib/build-linux/appimage/Dockerfile

@@ -17,13 +17,15 @@ COPY apt.preferences /etc/apt/preferences.d/snapshot
 
 RUN apt-get update -q && \
     apt-get install -qy --allow-downgrades \
+        sudo \
         git \
         wget \
         make \
         autotools-dev \
         autoconf \
         libtool \
         autopoint \
+        pkg-config \
         xz-utils \
         libssl-dev \
         libssl1.1 \
@@ -41,9 +43,10 @@ RUN apt-get update -q && \
         gettext \
         libzbar0 \
         libdbus-1-3 \
+        xutils-dev \
         libxkbcommon0 \
         libxkbcommon-x11-0 \
-        libxcb1 \
+        libxcb1-dev \
         libxcb-xinerama0 \
         libxcb-randr0 \
         libxcb-render0 \
@@ -56,6 +59,7 @@ RUN apt-get update -q && \
         libxcb-image0 \
         libxcb-keysyms1 \
         libxcb-util0 \
+        #libxcb-util1 \
         libxcb-render-util0 \
         libx11-xcb1 \
         libc6-dev \

contrib/build-linux/appimage/make_appimage.sh

@@ -71,6 +71,34 @@ tar xf "$CACHEDIR/Python-$PYTHON_VERSION.tar.xz" -C "$BUILDDIR"
 cp -f "$PROJECT_ROOT/electrum/libsecp256k1.so.0" "$APPDIR/usr/lib/libsecp256k1.so.0" || fail "Could not copy libsecp to its destination"
 
 
+# note: libxcb-util1 is not available in debian 10 (buster), only libxcb-util0. So we build it ourselves.
+#       This pkg is needed on some distros for Qt to launch. (see #8011)
+info "building libxcb-util1."
+XCB_UTIL_VERSION="acf790d7752f36e450d476ad79807d4012ec863b"
+# ^ git tag 0.4.0
+(
+    cd "$CACHEDIR"
+    mkdir "libxcb-util1"
+    cd "libxcb-util1"
+    if [ ! -d util ]; then
+        git clone --recursive "https://anongit.freedesktop.org/git/xcb/util"
+    fi
+    cd util
+    if ! $(git cat-file -e ${XCB_UTIL_VERSION}) ; then
+        info "Could not find requested version $XCB_UTIL_VERSION in local clone; fetching..."
+        git fetch --all
+        git submodule update
+    fi
+    git reset --hard
+    git clean -dfxq
+    git checkout "${XCB_UTIL_VERSION}^{commit}"
+    ./autogen.sh
+    ./configure --enable-shared
+    make -j4 -s || fail "Could not build libxcb-util1"
+    cp "$CACHEDIR/libxcb-util1/util/src/.libs/libxcb-util.so.1" "$APPDIR/usr/lib/libxcb-util.so.1"
+) || fail "Could build libxcb-util1"
+
+
 appdir_python() {
     env \
         PYTHONNOUSERSITE=1 \