Is it possible to make an AppImage of a cross-compiled application?

Hello everyone!

I’ve set up an environment for creating arm64 Linux binaries on an x86-64 host. This is simply Ubuntu amd64, configured for multiarch (dpkg --add-architecture arm64 and all that stuff.) Installing the libraries needed is done with:

apt-get install qtbase5-dev:arm64 libmpg123-dev:arm64 [etc...]

This installs the arm64 binaries of the libraries. Then I build by Qt application with:

aarch64-linux-gnu-qmake
make -j`nproc`

And I get a arm64 build of my application. Question now is, how on earth do I make an AppImage for it? If I try something like:

ARCH=arm_aarch64 linuxdeployqt \
    AppDir/usr/share/applications/nikos.chantziaras.qtads.desktop \
    -qmake=aarch64-linux-gnu-qmake

(linuxdeployqt is just a renamed linuxdeployqt-continuous-x86_64.AppImage.)

Then I get errors:

linuxdeployqt  (commit aeafcd2), build 13 built on 2022-01-28 22:37:07 UTC
Desktop file as first argument: "AppDir/usr/share/applications/nikos.chantziaras.qtads.desktop"
desktopExecEntry: "qtads"
desktopIconEntry: "qtads"
Found binary from desktop file: "/qtads/build/AppDir/usr/bin/qtads"
FHS-like mode with PREFIX, fhsPrefix: "/qtads/build/AppDir/usr"
app-binary: "/qtads/build/AppDir/usr/bin/qtads"
appDirPath: "/qtads/build/AppDir"
relativeBinPath: "usr/bin/qtads"
Copied "AppDir/usr/share/applications/nikos.chantziaras.qtads.desktop" to "/qtads/build/AppDir/nikos.chantziaras.qtads.desktop"
Found icons from desktop file: ("/qtads/build/AppDir/usr/share/icons/hicolor/256x256/apps/qtads.png", "/qtads/build/AppDir/usr/share/icons/hicolor/72x72/apps/qtads.png", "/qtads/build/AppDir/usr/share/icons/hicolor/48x48/apps/qtads.png")
iconToBeUsed: "/qtads/build/AppDir/usr/share/icons/hicolor/48x48/apps/qtads.png"
Copied "/qtads/build/AppDir/usr/share/icons/hicolor/48x48/apps/qtads.png" to "/qtads/build/AppDir/qtads.png"
ERROR: findDependencyInfo: ""
ERROR: findDependencyInfo: ""
WARNING: Could not find any external Qt libraries to deploy in "/qtads/build/AppDir"
WARNING: Perhaps linuxdeployqt was already used on "/qtads/build/AppDir" ?
WARNING: If so, you will need to rebuild "/qtads/build/AppDir" before trying again.
WARNING: Or ldd does not find the external Qt libraries but sees the system ones.
WARNING: If so, you will need to set LD_LIBRARY_PATH to the directory containing the external Qt libraries before trying again.
WARNING: FIXME: https://github.com/probonopd/linuxdeployqt/issues/2

Setting LD_LIBRARY_PATH to /usr/lib/aarch64-linux-gnu does not change anything.