Homebrew formula for official ghc 8.6.4 binaries

ghc.rb

class Ghc < Formula
  desc "Glorious Glasgow Haskell Compilation System"
  homepage "https://haskell.org/ghc/"
  url "https://downloads.haskell.org/~ghc/8.6.4/ghc-8.6.4-x86_64-apple-darwin.tar.xz"
  sha256 "cccb58f142fe41b601d73690809f6089f7715b6a50a09aa3d0104176ab4db09e"

  def install
    system "./configure", "--prefix=#{prefix}"

    ENV.deparallelize { system "make", "install" }
  end

  test do
    (testpath/"hello.hs").write('main = putStrLn "Hello Homebrew"')
    system "runghc", testpath/"hello.hs"
  end
end