Add a macOS Homebrew formula for Star Traders

This formula has been submitted to the upstream Homebrew homebrew-core
repository via https://github.com/Homebrew/homebrew-core/pull/46770

.gitattributes

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+trader.rb	ident

trader.rb

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+class Trader < Formula
+  desc "Star Traders"
+  homepage "https://www.zap.org.au/projects/trader/"
+  url "https://ftp.zap.org.au/pub/trader/unix/trader-7.13.tar.xz"
+  sha256 "0d2b51134166b0f436dc6423e2ce378b1df929a9de141c002f3da86af18bb262"
+
+  depends_on "pkg-config" => :build
+  depends_on "gettext"
+  depends_on "ncurses" # The system version does not work correctly
+
+  def install
+    ENV.prepend_path "PKG_CONFIG_PATH",
+        Formula["ncurses"].opt_libexec/"lib/pkgconfig"
+    args = %W[
+      --disable-dependency-tracking
+      --disable-silent-rules
+      --prefix=#{prefix}
+      --with-libintl-prefix=#{Formula["gettext"].opt_prefix}
+    ]
+    system "./configure", *args
+    system "make", "install"
+  end
+
+  test do
+    # Star Traders is an interactive game, so the only option for testing
+    # is to run something like "trader --version"
+    system "#{bin}/trader", "--version"
+  end
+end