File _constraints of Package enblend-enfuse

<!-- We build well with 2 CPUs/1.5GB, 3CPUs/2GB, 4CPUs/2.5GB-->
<constraints>
 <hardware>
  <physicalmemory>
   <size unit="M">1920</size>
  </physicalmemory>
  <processors>3</processors>
 </hardware>
</constraints>