aarch64: meson setup fails — singularity-gestures needs runtime/include, and its bootstrap is x86-64 only

[perlowja]

Summary

singularity-desktop cannot be configured on aarch64 as of d642160. meson setup fails before any compilation:

subprojects/singularity-gestures/meson.build:30:6: ERROR: Include dir runtime/include does not exist.

This is not architecture-specific in itself — the directory is absent on any
clean checkout — but the mechanism that populates it is x86-64 only, so arm64
has no way forward.

Why the directory is missing

singularity-gestures (51da49b) declares:

inc = include_directories('include', 'src', 'runtime/include')

but runtime/ contains exactly one tracked file:

$ git ls-files runtime/
runtime/.gitignore

$ cat runtime/.gitignore
*.so
*.task
*.onnx
include/

include/ is gitignored, so runtime/include is never in a checkout. It is
produced by scripts/bootstrap-runtime.sh, which downloads MediaPipe and ONNX
Runtime at build time.

Why arm64 cannot run that bootstrap

scripts/bootstrap-runtime.sh has no architecture detection at all — grep -c uname returns 0 — and hardcodes an x86-64 tarball:

"https://github.com/microsoft/onnxruntime/releases/download/v$onnx_version/onnxruntime-linux-x64-$onnx_version.tgz"

with onnx_dir="$download_dir/onnxruntime-linux-x64-$onnx_version". On aarch64
this fetches binaries for the wrong architecture. (I have not run it there —
the hardcoded -x64 URL and the absence of any arch branch are what I am
reporting, not a measured failure of the download itself.)

Upstream does publish onnxruntime-linux-aarch64-*.tgz for the same releases.

Why it blocks the whole tree

meson.build:13 pulls the subproject in unconditionally:

subproject('singularity-gestures')

There is no meson option to disable it (meson_options.txt has only
installer), so the failure is not confined to the gestures feature — the
entire desktop fails to configure.

Suggested fixes, roughly in order of effort

1. Select the ONNX Runtime tarball by uname -m, mapping aarch64 to the
   onnxruntime-linux-aarch64-* release asset.
2. Add a meson option (say gestures, defaulting to enabled) so a platform
   without the runtime can still build the desktop. This alone would unblock
   arm64 even without (1).
3. Have meson.build fail with a clear message pointing at
   scripts/bootstrap-runtime.sh when runtime/include is absent — the
   current error names a missing directory without saying it is generated.

Environment

• singularity-desktop d642160, singularity-gestures 51da49b
• aarch64 (CIX Sky1), Debian trixie build container
• meson/ninja from the distro; all other subprojects configure fine once this
  one is skipped

Workaround in use

Dropping the subproject('singularity-gestures') line from meson.build in
our build staging copy. That is a local build workaround, not a fix, and it
disables the gesture features entirely.

[perlowja]

Two additions after getting further into the build.

The Makefile pulls the bootstrap in independently of meson. Dropping the
subproject('singularity-gestures') line lets meson setup complete, but
make compile still fails, because gesture-runtime is a hard prerequisite in
two places:

Makefile:8   $(BUILD_DIR)/build.ninja: | gesture-runtime
Makefile:17  compile: gesture-runtime $(BUILD_DIR)/build.ninja labwc

So a meson option alone (suggestion 2 above) would not be sufficient — the make
rules need the same guard.

bootstrap-runtime.sh also hardcodes an interpreter path, independent of
the architecture problem:

subprojects/singularity-gestures/scripts/bootstrap-runtime.sh: line 27: /usr/bin/python3.12: No such file or directory
make: *** [Makefile:65: gesture-runtime] Error 127

Line 27 is /usr/bin/python3.12 -m venv .... Any image whose Python is not
exactly /usr/bin/python3.12 fails here before the x86-64 download is even
reached — Debian trixie ships 3.13, so this is not arm64-specific. python3
from PATH, or a command -v check, would fix it.

Worth noting the two failures mask each other: fixing only the architecture
would still leave the interpreter hardcode, and vice versa.

[mateoalfaro]

honestly i was looking into getting one of those snapdragon x laptops, so i may contribute towards arm support