gitlab-ci: Introduce aarch64-linux-llvm job
This nightly job will ensure that we don't break the LLVM backend on AArch64/Linux by bootstrapping GHC.
This would have caught #22640 (closed).
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This nightly job will ensure that we don't break the LLVM backend on AArch64/Linux by bootstrapping GHC.
This would have caught #22640 (closed).