Remove extra pthread switch

remove the extra pthread switch which might be there
  from the package config check for gthreads.

Signed-off-by: Peter Portante <peter.portante@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

configure

@@ -2083,7 +2083,16 @@ else
   for pthread_lib in $PTHREADLIBS_LIST; do
     if compile_prog "" "$pthread_lib" ; then
       pthread=yes
-      LIBS="$pthread_lib $LIBS"
+      found=no
+      for lib_entry in $LIBS; do
+        if test "$lib_entry" = "$pthread_lib"; then
+          found=yes
+          break
+        fi
+      done
+      if test "$found" = "no"; then
+        LIBS="$pthread_lib $LIBS"
+      fi
       break
     fi
   done