contrib: Fix change_prefix when used on binaries != libraries

extras/contrib/change_prefix.sh

@@ -48,12 +48,15 @@ files=`find . -type f`
 for file in $files; do 
  if test ".`file $file | grep Mach-O`" != "." ; then
     echo "Changing prefixes of '$file'"
+    islib=n
+    if test ".`file $file | grep 'Mach-O dynamically'`" != "." ; then
+      islib=y
+    fi
     libs=`otool -L $file 2>/dev/null | grep $prefix | cut -d\  -f 1`
-    WD=`pwd`
     first=y
     for i in "" $libs; do
       if ! test -z $i; then
-         if test $first = y; then
+        if test $islib = y -a $first = y; then
             install_name_tool -id `echo $i | sed -e "s,$prefix,$new_prefix,"` $file
             first=n
         else