message: In makefile, replace the format string "%06s" with "%06d" - portability fix.
diff: # The current MFEM version as an integer, see also `CMakeLists.txt`.
  MFEM_VERSION = 30300
  -MFEM_VERSION_STRING = $(shell printf "%06s" $(MFEM_VERSION) | \
  +MFEM_VERSION_STRING = $(shell printf "%06d" $(MFEM_VERSION) | \
  sed -e 's/^0*\(.*.\)\(..\)\(..\)$$/\1.\2.\3/' -e 's/\.0/./g' -e 's/\.0$$//')
  define MFEM_HELP_MSG
  