[Config] Normalize installation_root to ensure same character encoding

Some characters like "ü" where being represented as `["u", "̈"]` in
ruby < 2.3 and it caused errors down the line.

CHANGELOG.md

@@ -24,6 +24,11 @@ To install release candidates run `[sudo] gem install cocoapods --pre`
   [Jan Berkel](https://github.com/jberkel)
   [#5319](https://github.com/CocoaPods/CocoaPods/pull/5319)
 
+* Avoid removing all files when root directory contains unicode characters.  
+  [Marc Boquet](https://github.com/marcboquet)
+  [#5294](https://github.com/CocoaPods/CocoaPods/issues/5294)
+
+
 ## 1.0.0 (2016-05-10)
 
 ##### Enhancements

lib/cocoapods/config.rb

+require 'active_support/multibyte/unicode'
+
 module Pod
   # Stores the global configuration of CocoaPods.
   #
@@ -145,7 +147,8 @@ module Pod
     #         Podfile is located.
     #
     def installation_root
-      current_path = Pathname.pwd
+      current_dir = ActiveSupport::Multibyte::Unicode.normalize(Dir.pwd)
+      current_path = Pathname.new(current_dir)
       unless @installation_root
         until current_path.root?
           if podfile_path_in_dir(current_path)

spec/unit/config_spec.rb

@@ -112,6 +112,15 @@ module Pod
         end
       end
 
+      it 'returns the working directory correctly when it includes unicode characters' do
+        unicode_directory = temporary_directory + "ü"
+        FileUtils.mkdir(unicode_directory)
+        Dir.chdir(unicode_directory) do
+          File.open('Podfile', 'w') {}
+          @config.installation_root.to_s.should == unicode_directory.to_s
+        end
+      end
+
       before do
         @config.installation_root = temporary_directory
       end