In order to build the mesa llvmpipe driver for Android, LLVM libraries
for Android are needed, but building them each time a new upstream mesa
is built would be too much overhead.
So add a script to build LLVM libraries for Android and call it from the
debian/android_build job. The actual build will be performed only when
necessary and the resulting artifact will be uploaded to the S3 bucket
to be re-used when building mesa for Android.
The build process follows what has been documented in
docs/drivers/llvmpipe.rst
Reviewed-by: Guilherme Gallo <guilherme.gallo@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/31093>
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