A number of cmake configuration fixes for SPEC.

Description

A number of cmake configuration fixes for SPEC.

These changes were needed to make the spec 2000 and spec 2006 benchmark
compile correctly on the following platforms, that I used for testing:

  • Ubuntu 12.04LTS x86_64, gcc 4.7
  • Ubuntu 12.04LTS x86_64, clang 3.5
  • Debian linux AArch64 v8.0, clang 3.7
  • Debian linux AArch32 v8.0, clang 3.7
  • OSX Yosemite x86_64, Xcode clang 7.0.0

Differential Revision: http://reviews.llvm.org/D16688

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