Juan 27/10/2023:Rules.LXgfortran.mk, managed defaut value CC=gcc + FC=gfortran...

Juan 27/10/2023:Rules.LXgfortran.mk, managed defaut value CC=gcc + FC=gfortran <=> default wrong old CC=cc + FC=f77

src/Rules.LXgfortran.mk

@@ -74,9 +74,17 @@ CXXFLAGS = $(OPT_OPENACC)
 #$(OBJS_REPROD) : OPT = $(OPT_BASE) $(OPT_OPENACC) $(OPT_PERF2) -Mvect=nosimd -Minfo=all -g
 endif
 #
-CC ?= gcc
-CXX ?= g++
-FC ?= gfortran 
+ifneq ($(origin CC),environment)
+# default value CC=cc not correct for gnu compiler
+CC = gcc
+endif
+ifneq ($(origin CXX),environment)
+CXX = g++
+endif
+ifneq ($(origin FC),environment)
+# default value FC=f77 not correct for gnu compiler
+FC = gfortran
+endif
 
 #   Gfortran version
 GFV=$(shell  $(F90) --version | grep -E -m1 -o ' [[:digit:]\.]{2,}( |$$)'  | sed 's/\.//g' )