The build is unreachable.

Build log

> /tmp/stackage-build2452$ stack unpack zstd-0.1.0.0@sha256:e04dd898175aefb278be634ce18bd57ccb3e364e660b0890b1eb84f3437fcac2
Unpacked zstd-0.1.0.0 to /tmp/stackage-build2452/zstd-0.1.0.0/
> /tmp/stackage-build2452/zstd-0.1.0.0$ 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/zstd-0.1.0.0$ ./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/zstd-0.1.0.0 --htmldir=/home/circleci/project/builds/nightly/doc/zstd-0.1.0.0 --haddockdir=/home/circleci/project/builds/nightly/doc/zstd-0.1.0.0
Configuring zstd-0.1.0.0...
> /tmp/stackage-build2452/zstd-0.1.0.0$ ghc -clear-package-db -global-package-db -package-db=/home/circleci/project/builds/nightly/pkgdb Setup
> /tmp/stackage-build2452/zstd-0.1.0.0$ ./Setup build
Preprocessing library for zstd-0.1.0.0..
Building library for zstd-0.1.0.0..
[ 1 of 10] Compiling Codec.Compression.Zstd.FFI.Types ( dist/build/Codec/Compression/Zstd/FFI/Types.hs, dist/build/Codec/Compression/Zstd/FFI/Types.o )
[ 2 of 10] Compiling Codec.Compression.Zstd.FFI ( Codec/Compression/Zstd/FFI.hs, dist/build/Codec/Compression/Zstd/FFI.o )
[ 3 of 10] Compiling Codec.Compression.Zstd.Base.Types ( Codec/Compression/Zstd/Base/Types.hs, dist/build/Codec/Compression/Zstd/Base/Types.o )
[ 4 of 10] Compiling Codec.Compression.Zstd.Base ( Codec/Compression/Zstd/Base.hs, dist/build/Codec/Compression/Zstd/Base.o )
[ 5 of 10] Compiling Codec.Compression.Zstd.Streaming ( Codec/Compression/Zstd/Streaming.hs, dist/build/Codec/Compression/Zstd/Streaming.o )

Codec/Compression/Zstd/Streaming.hs:98:10: warning: [-Wincomplete-patterns]
    Pattern match(es) are non-exhaustive
    In a multi-way if alternative:
        Guards do not cover entire pattern space
   |
98 |       if | leftover == 0 -> do
   |          ^^^^^^^^^^^^^^^^^^^^^...
[ 6 of 10] Compiling Codec.Compression.Zstd.Lazy ( Codec/Compression/Zstd/Lazy.hs, dist/build/Codec/Compression/Zstd/Lazy.o )
[ 7 of 10] Compiling Codec.Compression.Zstd.Types ( Codec/Compression/Zstd/Types.hs, dist/build/Codec/Compression/Zstd/Types.o )
[ 8 of 10] Compiling Codec.Compression.Zstd.Internal ( Codec/Compression/Zstd/Internal.hs, dist/build/Codec/Compression/Zstd/Internal.o )
[ 9 of 10] Compiling Codec.Compression.Zstd.Efficient ( Codec/Compression/Zstd/Efficient.hs, dist/build/Codec/Compression/Zstd/Efficient.o )
[10 of 10] Compiling Codec.Compression.Zstd ( Codec/Compression/Zstd.hs, dist/build/Codec/Compression/Zstd.o )
> /tmp/stackage-build2452/zstd-0.1.0.0$ ghc -clear-package-db -global-package-db -package-db=/home/circleci/project/builds/nightly/pkgdb Setup
> /tmp/stackage-build2452/zstd-0.1.0.0$ ./Setup copy
Installing library in /home/circleci/project/builds/nightly/lib/x86_64-linux-ghc-8.7.20181119/zstd-0.1.0.0-3DbDLaKQgtAKcU2ZIw0QFl
> /tmp/stackage-build2452/zstd-0.1.0.0$ ghc -clear-package-db -global-package-db -package-db=/home/circleci/project/builds/nightly/pkgdb Setup
> /tmp/stackage-build2452/zstd-0.1.0.0$ ./Setup register
Registering library for zstd-0.1.0.0..