message: make config: allow specifying a compiler to compile get_hypre_version
  this fixes configs in supercomputers when login nodes != backend nodes
diff: @@ -36,6 +36,7 @@ CONFIG_MK = config.mk
  all: header config-mk
  MPI = $(MFEM_USE_MPI:NO=)
  +GHV_CXX ?= $(MFEM_CXX)
  GHV = get_hypre_version
  GHV_FLAGS = $(subst @MFEM_DIR@,$(if $(MFEM_DIR),$(MFEM_DIR),..),$(HYPRE_OPT))
  SMX = $(if $(MFEM_USE_PUMI:NO=),MFEM_USE_SIMMETRIX)
  @@ -44,7 +45,7 @@ SMX_FILE = $(subst @MFEM_DIR@,$(if $(MFEM_DIR),$(MFEM_DIR),..),$(SMX_PATH))
  $(GHV): $(SRC)$(GHV).cpp
  $(call mfem-info, Determining HYPRE version ...)
  - $(MFEM_CXX) ${GHV_FLAGS} $(SRC)$(GHV).cpp -o $(GHV)
  + $(GHV_CXX) ${GHV_FLAGS} $(SRC)$(GHV).cpp -o $(GHV)
  $(GHV).out: $(GHV)
  ./$(GHV) > $(GHV).out
  .INTERMEDIATE: $(GHV) $(GHV).out
  