Add ghc package

packages/ghc.rb

+require 'package'
+
+class Ghc < Package
+  description 'The Glasgow Haskell Compiler is a state-of-the-art, open source compiler and interactive environment for the functional language Haskell.'
+  homepage 'https://www.haskell.org/ghc/'
+  version '8.2.2'
+  source_url 'https://www.haskell.org/ghc/download_ghc_8_2_2.html'
+  source_sha256 'faceb0629054cc52ba70abad9179564df8dcbc0f9349df85698966047c274f7a'
+
+  binary_url ({
+  })
+  binary_sha256 ({
+  })
+
+  depends_on 'stack'
+  depends_on 'libtinfo'
+
+  def self.build
+    system "stack setup ghc-8.2.2"
+    system "echo '#!/bin/bash' > ghc"
+    system "echo 'stack ghc \"\$@\"' >> ghc"
+  end
+
+  def self.install
+    system "install -Dm755 ghc #{CREW_DEST_PREFIX}/bin/ghc"
+  end
+end