Verify code-signature after installation.

lib/xcode/install.rb

@@ -90,6 +90,10 @@ def install_dmg(dmgPath, suffix = '', switch = true, clean = true, components =
       `sudo ditto "#{source}" "#{xcode_path}"`
       `umount "/Volumes/Xcode"`
 
+      if not verify_integrity(xcode_path)
+        `sudo rm -f #{xcode_path}`
+      end
+
       enable_developer_mode
       `sudo xcodebuild -license` unless xcode_license_approved?
       install_components(xcode_path) if components
@@ -240,6 +244,11 @@ def seedlist
       xcodes || fetch_seedlist
     end
 
+    def verify_integrity(path)
+      puts `codesign --verify --verbose #{path}`
+      $?.exitstatus == 0
+    end
+
     def xcode_license_approved?
       !(`/usr/bin/xcrun clang 2>&1` =~ /license/ && !$CHILD_STATUS.success?)
     end