dog: add linux-only dependencies

Formula/dog.rb

@@ -18,6 +18,11 @@ class Dog < Formula
   depends_on "pandoc" => :build
   depends_on "rust" => :build
 
+  on_linux do
+    depends_on "pkg-config" => :build
+    depends_on "openssl@1.1"
+  end
+
   def install
     system "cargo", "install", *std_cargo_args
     bash_completion.install "completions/dog.bash" => "dog"