[DynInst_API:] [dyninst/dyninst] 7186be: Use OpenMP target (#1339)

[Tim Haines <noreply@xxxxxxxxxx>]

  Branch: refs/heads/cmake_modernization
  Home:   https://github.com/dyninst/dyninst
  Commit: 7186be5098ff2f4ec1e2440a0ff18bbaf9b7fb17
      https://github.com/dyninst/dyninst/commit/7186be5098ff2f4ec1e2440a0ff18bbaf9b7fb17
  Author: Tim Haines <thaines.astro@xxxxxxxxx>
  Date:   2022-12-14 (Wed, 14 Dec 2022)

  Changed paths:
    M CMakeLists.txt
    M common/CMakeLists.txt
    M parseAPI/CMakeLists.txt
    M parseThat/CMakeLists.txt
    M symtabAPI/CMakeLists.txt

  Log Message:
  -----------
  Use OpenMP target (#1339)

This also provides a dummy target so we don't have to do any additional checking when USE_OpenMP=OFF. We only use OpenMP_CXX, so I didn't create a target for the other languages (C,Fortran).