keg: Skip relocation when dylib ID/install name doesn't change.

Library/Homebrew/os/mac/keg.rb

@@ -1,5 +1,6 @@
 class Keg
   def change_dylib_id(id, file)
+    return if file.dylib_id == id
     @require_relocation = true
     puts "Changing dylib ID of #{file}\n  from #{file.dylib_id}\n    to #{id}" if ARGV.debug?
     MachO::Tools.change_dylib_id(file, id, strict: false)
@@ -13,6 +14,7 @@ class Keg
   end
 
   def change_install_name(old, new, file)
+    return if old == new
     @require_relocation = true
     puts "Changing install name in #{file}\n  from #{old}\n    to #{new}" if ARGV.debug?
     MachO::Tools.change_install_name(file, old, new, strict: false)