File _constraints of Package libfabric

<?xml version="1.0"?>
<constraints>
  <overwrite>
    <conditions>
      <arch>i586</arch>
      <arch>x86_64</arch>
    </conditions>
    <hardware>
      <cpu>
        <flag>sse4_2</flag>
      </cpu>
    </hardware>
  </overwrite>
</constraints>