### Please describe the problem.

brew install git-annex failed.

### What steps will reproduce the problem?


### What version of git-annex are you using? On what operating system?
Mac OS X 10.11 El Capitan

### Please provide any additional information below.

[[!format sh """
95b3d57ce7--git-annex-7.20191230.tar.gz
==> cabal v1-sandbox init
==> cabal v1-update
==> cabal v1-install --jobs=4 --max-backjumps=100000 alex
==> cabal v1-install --jobs=4 --max-backjumps=100000 happy
==> cabal v1-install --jobs=4 --max-backjumps=100000 c2hs
==> cabal v1-install --jobs=4 --max-backjumps=100000 --only-dependencies --constraint http-conduit>=2.3 --constraint net
==> cabal v1-configure --flags=s3 webapp
==> cabal v1-install --jobs=4 --max-backjumps=100000 --prefix=/usr/local/Cellar/git-annex/7.20191230 --constraint http-c
Last 15 lines from /Users/choi/Library/Logs/Homebrew/git-annex/08.cabal:
StandaloneDeriving

Please enable the extensions by copy/pasting these lines into the top of your file:

{-# LANGUAGE DerivingStrategies #-}
{-# LANGUAGE StandaloneDeriving #-}
   |
31 | share [mkPersist sqlSettings, mkMigrate "migrateKeysDb"] [persistLowerCase|
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^...
cabal: Leaving directory '.'
cabal: Error: some packages failed to install:
git-annex-7.20191230-JGm7b2Gk5I8w0hi2BDCiw failed during the building phase.
The exception was:
ExitFailure 1


Do not report this issue to Homebrew/brew or Homebrew/core!

These open issues may also help:
git-annex-remote-rclone 0.6 (new formula) https://github.com/Homebrew/homebrew-core/pull/49468
git-annex: add OBJC_DISABLE_INITIALIZE_FORK_SAFETY environment variable https://github.com/Homebrew/homebrew-core/pull/48411
"""]]

### Have you had any luck using git-annex before? (Sometimes we get tired of reading bug reports all day and a lil' positive end note does wonders)