Add cabal-install binaries (required for GHC 8.10.1)

36 jobs for c-i-3-2 in 27 minutes and 47 seconds (queued for 20 minutes and 23 seconds)
Name Stage Failure
test:shellcheck Test
+ export PATH=/builds/trac-bpfoley/ghcup/.ghcup/bin:/builds/trac-bpfoley/ghcup/.local/bin:/home/ghc/.cabal/bin:/opt/llvm/bin:/home/ghc/.local/bin:/opt/cabal/2.4/bin:/opt/ghc/8.4.4/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
+ shellcheck ghcup
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ERROR: Job failed: exit code 1