Fixing mistake in elemental_sub.cmake with respect to export CXX_FLAGS.
Fixing mistake in elemental_sub.cmake with respect to export CXX_FLAGS.

birm/Elemental,justusc/Elemental,sg0/Elemental,mcopik/Elemental,justusc/Elemental,sg0/Elemental,sg0/Elemental,mcopik/Elemental,sg0/Elemental,birm/Elemental,sg0/Elemental,mcopik/Elemental,justusc/Elemental,justusc/Elemental,mcopik/Elemental,sg0/Elemental,justusc/Elemental,birm/Elemental,birm/Elemental,birm/Elemental,justusc/Elemental,birm/Elemental,mcopik/Elemental,mcopik/Elemental