rust: Fix rustlib dylib IDs in post_install.

This is the less invasive version of Homebrew/brew#2764.

Author: woodruffw

Formula/rust.rb

@@ -19,6 +19,7 @@ class Rust < Formula
   end
 
   bottle do
+    rebuild 1
     sha256 "330dd281718d164d7415d83a6a8376cb2cc161ecee82e3fb6ba869a885b7fe8b" => :sierra
     sha256 "c90ae66966ab11382c50fc49c8ddb6320aa34390f3e76081a592e39a7e48a9fa" => :el_capitan
     sha256 "b0cfdaeb92b85192846d864f20fb6ca3a162163fb549918a223b4eef4eae3d91" => :yosemite
@@ -101,6 +102,13 @@ def install
     rm_rf prefix/"lib/rustlib/install.log"
   end
 
+  def post_install
+    Dir[prefix/"lib/rustlib/**/*.dylib"].each do |dylib|
+      chmod 0755, dylib
+      MachO::Tools.change_dylib_id(dylib, "@rpath/#{File.basename(dylib)}")
+    end
+  end
+
   test do
     system "#{bin}/rustdoc", "-h"
     (testpath/"hello.rs").write <<-EOS.undent