The build is unreachable.

Build log

> /tmp/stackage-build2455$ stack unpack stringbuilder-0.5.1@sha256:87481cbbb6324acc00dec6ad715662e2177adcdc69224941011f1c1730e4debe
Unpacked stringbuilder-0.5.1 to /tmp/stackage-build2455/stringbuilder-0.5.1/
> /tmp/stackage-build2455/stringbuilder-0.5.1$ 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-build2455/stringbuilder-0.5.1$ ./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/stringbuilder-0.5.1 --htmldir=/home/circleci/project/builds/nightly/doc/stringbuilder-0.5.1 --haddockdir=/home/circleci/project/builds/nightly/doc/stringbuilder-0.5.1
Configuring stringbuilder-0.5.1...
> /tmp/stackage-build2455/stringbuilder-0.5.1$ ghc -clear-package-db -global-package-db -package-db=/home/circleci/project/builds/nightly/pkgdb Setup
> /tmp/stackage-build2455/stringbuilder-0.5.1$ ./Setup build
Preprocessing library for stringbuilder-0.5.1..
Building library for stringbuilder-0.5.1..
[1 of 1] Compiling Data.String.Builder ( src/Data/String/Builder.hs, dist/build/Data/String/Builder.o )

src/Data/String/Builder.hs:24:1: warning: [-Wunused-imports]
    The import of ‘Control.Applicative’ is redundant
      except perhaps to import instances from ‘Control.Applicative’
    To import instances alone, use: import Control.Applicative()
   |
24 | import           Control.Applicative
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

src/Data/String/Builder.hs:26:1: warning: [-Wunused-imports]
    The import of ‘Data.Monoid’ is redundant
      except perhaps to import instances from ‘Data.Monoid’
    To import instances alone, use: import Data.Monoid()
   |
26 | import           Data.Monoid
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> /tmp/stackage-build2455/stringbuilder-0.5.1$ ghc -clear-package-db -global-package-db -package-db=/home/circleci/project/builds/nightly/pkgdb Setup
> /tmp/stackage-build2455/stringbuilder-0.5.1$ ./Setup copy
Installing library in /home/circleci/project/builds/nightly/lib/x86_64-linux-ghc-8.7.20181122/stringbuilder-0.5.1-3Ytv9WhMjql9nZxJircNkI
> /tmp/stackage-build2455/stringbuilder-0.5.1$ ghc -clear-package-db -global-package-db -package-db=/home/circleci/project/builds/nightly/pkgdb Setup
> /tmp/stackage-build2455/stringbuilder-0.5.1$ ./Setup register
Registering library for stringbuilder-0.5.1..