rdesktop: use Homebrew's openssl

Formula/rdesktop.rb

@@ -5,6 +5,7 @@ class Rdesktop < Formula
   url 'https://downloads.sourceforge.net/project/rdesktop/rdesktop/1.8.1/rdesktop-1.8.1.tar.gz'
   sha1 '57bb41f98ddf9eeef875c613d790fee37971d0f8'
 
+  depends_on "openssl"
   depends_on :x11
 
   patch :DATA
@@ -13,7 +14,7 @@ class Rdesktop < Formula
     args = ["--prefix=#{prefix}",
             "--disable-credssp",
             "--disable-smartcard", # disable temporally before upstream fix
-            "--with-openssl=#{MacOS.sdk_path}/usr",
+            "--with-openssl=#{Formula["openssl"].opt_prefix}",
             "--x-includes=#{MacOS::X11.include}",
             "--x-libraries=#{MacOS::X11.lib}"]
     system "./configure", *args