The build is unreachable.

Build log

> /tmp/stackage-build2452$ stack unpack cereal-0.5.7.0@sha256:550af4aee27b8cbf11e930169af26a8b5da7fa3d456290986f65c727f5b41cd0
Unpacked cereal-0.5.7.0 to /tmp/stackage-build2452/cereal-0.5.7.0/
> /tmp/stackage-build2452/cereal-0.5.7.0$ ghc -clear-package-db -global-package-db -package-db=/home/circleci/project/builds/nightly/pkgdb Setup
[1 of 1] Compiling Main             ( Setup.hs, Setup.o )
Linking Setup ...
> /tmp/stackage-build2452/cereal-0.5.7.0$ ./Setup configure --package-db=clear --package-db=global --package-db=/home/circleci/project/builds/nightly/pkgdb --libdir=/home/circleci/project/builds/nightly/lib --bindir=/home/circleci/project/builds/nightly/bin --datadir=/home/circleci/project/builds/nightly/share --libexecdir=/home/circleci/project/builds/nightly/libexec --sysconfdir=/home/circleci/project/builds/nightly/etc --docdir=/home/circleci/project/builds/nightly/doc/cereal-0.5.7.0 --htmldir=/home/circleci/project/builds/nightly/doc/cereal-0.5.7.0 --haddockdir=/home/circleci/project/builds/nightly/doc/cereal-0.5.7.0
Configuring cereal-0.5.7.0...
> /tmp/stackage-build2452/cereal-0.5.7.0$ ghc -clear-package-db -global-package-db -package-db=/home/circleci/project/builds/nightly/pkgdb Setup
> /tmp/stackage-build2452/cereal-0.5.7.0$ ./Setup build
Preprocessing library for cereal-0.5.7.0..
Building library for cereal-0.5.7.0..
[1 of 4] Compiling Data.Serialize.Get ( src/Data/Serialize/Get.hs, dist/build/Data/Serialize/Get.o )
[2 of 4] Compiling Data.Serialize.Put ( src/Data/Serialize/Put.hs, dist/build/Data/Serialize/Put.o )
[3 of 4] Compiling Data.Serialize.IEEE754 ( src/Data/Serialize/IEEE754.hs, dist/build/Data/Serialize/IEEE754.o )
[4 of 4] Compiling Data.Serialize   ( src/Data/Serialize.hs, dist/build/Data/Serialize.o )

src/Data/Serialize.hs:290:9: warning: [-Wincomplete-patterns]
    Pattern match(es) are non-exhaustive
    In an equation for ‘findNr’: Patterns not matched: _ _
    |
290 |         findNr lo hi
    |         ^^^^^^^^^^^^...
> /tmp/stackage-build2452/cereal-0.5.7.0$ ghc -clear-package-db -global-package-db -package-db=/home/circleci/project/builds/nightly/pkgdb Setup
> /tmp/stackage-build2452/cereal-0.5.7.0$ ./Setup copy
Installing library in /home/circleci/project/builds/nightly/lib/x86_64-linux-ghc-8.7.20181122/cereal-0.5.7.0-15nJbzQragxLXxMZb0dF9G
> /tmp/stackage-build2452/cereal-0.5.7.0$ ghc -clear-package-db -global-package-db -package-db=/home/circleci/project/builds/nightly/pkgdb Setup
> /tmp/stackage-build2452/cereal-0.5.7.0$ ./Setup register
Registering library for cereal-0.5.7.0..