use ls instead of find to avoid incompatibility with gnu find

plugins/xcode/xcode.plugin.zsh

 #xc function courtesy of http://gist.github.com/subdigital/5420709
 function xc {
-  xcode_proj=`find . -name "*.xc*" -d 1 | sort -r | head -1`
+  xcode_proj=`ls | grep "\.xc" | sort -r | head -1`
   if [[ `echo -n $xcode_proj | wc -m` == 0 ]]
   then
     echo "No xcworkspace/xcodeproj file found in the current directory."