[DynInst_API:] [dyninst/dyninst] b69554: Allow CMake files for dependencies to be included ...

[Tim Haines <noreply@xxxxxxxxxx>]

  Branch: refs/heads/master
  Home:   https://github.com/dyninst/dyninst
  Commit: b69554bd2c70260298d609af95bb2f3a43a9893a
      https://github.com/dyninst/dyninst/commit/b69554bd2c70260298d609af95bb2f3a43a9893a
  Author: Tim Haines <thaines.astro@xxxxxxxxx>
  Date:   2019-09-07 (Sat, 07 Sep 2019)

  Changed paths:
    M cmake/Boost.cmake
    M cmake/ElfUtils.cmake
    M cmake/LibIberty.cmake
    M cmake/ThreadingBuildingBlocks.cmake

  Log Message:
  -----------
  Allow CMake files for dependencies to be included multiple times (#639)

Previously, multiple inclusions would result in the library being looked
up or downloaded/built multiple times. This ensures these actions happen
only once.