Fix cog cask postflight xattr path to use actual binary name (#32)

The postflight block referenced staged_path/cog, but the downloaded
binary retains its original name (cog_Darwin_arm64 or cog_Darwin_x86_64)
in the staged directory. The binary stanza only creates a symlink with
the target name, it does not rename the source file.

This caused 'xattr -dr com.apple.quarantine' to fail with
'No such file' on every install.

Author: markphelps

Casks/cog.rb

@@ -26,7 +26,8 @@
                        end}", target: "cog"
 
   postflight do
+    binary_name = "cog_Darwin_#{Hardware::CPU.arm? ? "arm64" : "x86_64"}"
     system_command "/usr/bin/xattr",
-                   args: ["-dr", "com.apple.quarantine", "#{staged_path}/cog"]
+                   args: ["-dr", "com.apple.quarantine", "#{staged_path}/#{binary_name}"]
   end
 end