Unable to Install on OSX 10.14.3 (Mojave)

[Cmdv]

Describe the bug
Unsure if related to #38 but when building using Stack to install on OSX 10.14.3, running stack install

To Reproduce
Steps to reproduce the behavior:

1. Brew install ....
2. stack build happy
3. stack install
4. See error messages

Expected behavior
Should build :)

Error Messages

Package libffi was not found in the pkg-config search path.
    Perhaps you should add the directory containing `libffi.pc'
    to the PKG_CONFIG_PATH environment variable
    Package 'libffi', required by 'gobject-introspection-1.0', not found

So I tried to install manually with stack build libffi and was received following error:

Configuring libffi-0.1...
    clang: warning: argument unused during compilation: '-nopie' [-Wunused-command-line-argument]
    Cabal-simple_mPHDZzAJ_2.2.0.1_ghc-8.4.3: The pkg-config package 'libffi' is
    required but it could not be found.

so thought I'll try stack build on it's own and the following error is shown:

Configuring haskell-gi-0.21.3...
    clang: warning: argument unused during compilation: '-nopie' [-Wunused-command-line-argument]
    Cabal-simple_mPHDZzAJ_2.2.0.1_ghc-8.4.3: '/usr/local/bin/pkg-config' exited
    with an error:
    Package libffi was not found in the pkg-config search path.
    Perhaps you should add the directory containing `libffi.pc'
    to the PKG_CONFIG_PATH environment variable
    Package 'libffi', required by 'gobject-introspection-1.0', not found

Desktop (please complete the following information):

• OS: OSX 10.14.3
• Komposition v ?? (latest as of 7 jan 2018)
• Build environment Stack

[owickstrom]

Hi! This looks like you're missing some system dependencies. I see you have run brew install, but it might be that the list of dependencies at https://owickstrom.github.io/komposition/user-guide/installation/#macos is incomplete. Can you try installing libffi with Homebrew?

[Cmdv]

🎉 that worked, wasn't sure where the library came from so assumed it was a Haskell one!
I then noticed that libffi was missing from the install script in the docs and probably why it didn't install in the first place.