kafkacat: add optional json support

Closes Homebrew/homebrew#48463.

Signed-off-by: Dominyk Tiller <dominyktiller@gmail.com>

Formula/kafkacat.rb

@@ -11,11 +11,20 @@ class Kafkacat < Formula
     sha256 "a66d6d312498e117d485d7eea58e412da287be1dc08a1be0cd621d6a77763c7f" => :mavericks
   end
 
+  option "with-yajl", "Adds JSON support"
+
   depends_on "librdkafka"
+  depends_on "yajl" => :optional
 
   def install
-    system "./configure", "--disable-dependency-tracking",
-                          "--prefix=#{prefix}"
+    args = %W[
+      --disable-dependency-tracking
+      --prefix=#{prefix}
+    ]
+
+    args << "--enable-json" if build.with?("yajl")
+
+    system "./configure", *args
     system "make"
     system "make", "install"
   end