FlightRecorder.cc breaks compilation for --enable-comms=none

[leonhostetler]

Trying to compile with --enable-comms=none fails with an error like:

	  CXX      util/FlightRecorder.o
	../../Grid/util/FlightRecorder.cc: In static member function ‘static void Grid::FlightRecorder::xmitLog(void*, uint64_t)’:
	../../Grid/util/FlightRecorder.cc:293:17: error: ‘MPI_COMM_WORLD’ was not declared in this scope
	  293 |     MPI_Barrier(MPI_COMM_WORLD);
	      |                 ^~~~~~~~~~~~~~
	../../Grid/util/FlightRecorder.cc:293:5: error: ‘MPI_Barrier’ was not declared in this scope
	  293 |     MPI_Barrier(MPI_COMM_WORLD);
	      |     ^~~~~~~~~~~

Replacing the line

MPI_Barrier(MPI_COMM_WORLD);

in Grid/util/FlightRecorder.cc with

    #if defined (GRID_COMMS_MPI) || defined (GRID_COMMS_MPI3) || defined (GRID_COMMS_MPIT)
    MPI_Barrier(MPI_COMM_WORLD);
    #endif

lets it compile, but I don't know if that would break something else or not.

[leonhostetler]

Fixed by commit 8a09888