Foward CMAKE_TOOLCHAIN_FILE to arrow build for sdk cross-compilation (

#7866)

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### What

Add `-DCMAKE_TOOLCHAIN_FILE=${CMAKE_TOOLCHAIN_FILE}` to the cmake file
to fix #7445

### Checklist
* [x] I have read and agree to [Contributor
Guide](https://github.com/rerun-io/rerun/blob/main/CONTRIBUTING.md) and
the [Code of
Conduct](https://github.com/rerun-io/rerun/blob/main/CODE_OF_CONDUCT.md)
* [x] I've included a screenshot or gif (if applicable)
* [x] I have tested the web demo (if applicable):
* Using examples from latest `main` build:
[rerun.io/viewer](https://rerun.io/viewer/pr/7866?manifest_url=https://app.rerun.io/version/main/examples_manifest.json)
* Using full set of examples from `nightly` build:
[rerun.io/viewer](https://rerun.io/viewer/pr/7866?manifest_url=https://app.rerun.io/version/nightly/examples_manifest.json)
* [x] The PR title and labels are set such as to maximize their
usefulness for the next release's CHANGELOG
* [x] If applicable, add a new check to the [release
checklist](https://github.com/rerun-io/rerun/blob/main/tests/python/release_checklist)!
* [x] If have noted any breaking changes to the log API in
`CHANGELOG.md` and the migration guide

- [PR Build Summary](https://build.rerun.io/pr/7866)
- [Recent benchmark results](https://build.rerun.io/graphs/crates.html)
- [Wasm size tracking](https://build.rerun.io/graphs/sizes.html)

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---------

Co-authored-by: Emil Ernerfeldt <emil.ernerfeldt@gmail.com>

rerun_cpp/download_and_build_arrow.cmake

@@ -100,6 +100,7 @@ function(download_and_build_arrow)
         -Dxsimd_SOURCE=BUNDLED
         -DBOOST_SOURCE=BUNDLED
         -DARROW_BOOST_USE_SHARED=OFF
+        -DCMAKE_TOOLCHAIN_FILE=${CMAKE_TOOLCHAIN_FILE} # Specify the toolchain file for cross-compilation (see https://github.com/rerun-io/rerun/issues/7445)
         SOURCE_SUBDIR cpp
         BUILD_BYPRODUCTS ${ARROW_LIBRARY_FILE} ${ARROW_BUNDLED_DEPENDENCIES_FILE}
     )