[cvc4] (3 commits) ...Merge changes from Dan Horák to fix secondary arch builds.

[Jerry James]

Summary of changes:

  6f20269... allow build without gperftools (*)
  ee6164b... catch also s390{,x} whose triplet is s390{,x}-ibm-linux-gnu (*)
  4ead8ba... Merge changes from Dan Horák to fix secondary arch builds.

(*) This commit already existed in another branch; no separate mail sent