message: Temporarily disabling MPI on toss3 clang configurations.  Workaround for
  There is a known configuration error with LC's compiler configurations with Cland and MPI on toss3.
  This commit temporarily disables MPI on clang builds until the issue is resolved.
diff: ##############################################################################
  # MPI - manually added for now
  ##############################################################################
  -set(ENABLE_MPI ON CACHE PATH "")
  +
  +# Temporarily disabling MPI on toss3 clang. See JIRA issue ATK-1017.
  +set(ENABLE_MPI OFF BOOL PATH "")
  +
  set(MPI_HOME "/usr/tce/packages/mvapich2/mvapich2-2.2-clang-3.9.0/" CACHE PATH "")
  set(MPI_C_COMPILER "${MPI_HOME}/bin/mpicc" CACHE PATH "")
  set(MPI_CXX_COMPILER "${MPI_HOME}/bin/mpicxx" CACHE PATH "")
  