brew doctor: update expat check

Apaprently both expat.framework and libexpat.framework exist
and interfere with CMake.

Library/Homebrew/cmd/doctor.rb

@@ -574,15 +574,17 @@ end
 
 def check_for_other_frameworks
   # Other frameworks that are known to cause problems when present
-  if File.exist? "/Library/Frameworks/expat.framework"
-    puts <<-EOS.undent
-      /Library/Frameworks/expat.framework detected
+  ["/Library/Frameworks/expat.framework", "/Library/Frameworks/libexpat.framework"].each do |f|
+    if File.exist? f
+      puts <<-EOS.undent
+        #{f} detected
 
-      This will be picked up by Cmake's build system and likey cause the
-      build to fail, trying to link to a 32-bit version of expat.
-      You may need to move this file out of the way to compile Cmake.
+        This will be picked up by Cmake's build system and likey cause the
+        build to fail, trying to link to a 32-bit version of expat.
+        You may need to move this file out of the way to compile Cmake.
 
-    EOS
+      EOS
+    end
   end
 end