Improve Makefile (no unneeded recompilation of executables)

Makefile

 # Executables
 EXECUTABLES = $(patsubst %.$(SRC_EXT), $(BIN_DIR)/%, $(notdir $(SOURCES_EXECS)))
 
+# Executables (parallel)
+EXECUTABLES_PAR = $(patsubst %.$(SRC_EXT), $(BIN_DIR)/%, $(notdir $(SOURCES_EXECS_PAR)))
+
 
 # Main target: all executables (and thus the library, and thus all objects)
 all: $(EXECUTABLES)
 
 # Build executables
-$(EXECUTABLES): $(BIN_DIR)/%: $(SRC_DIR)/EXECS/%.$(SRC_EXT) lib$(VERSION).a
+$(EXECUTABLES): $(BIN_DIR)/%: $(SRC_DIR)/EXECS/%.$(SRC_EXT) $(LIB_DIR)/lib$(VERSION).a
 	$(COMPILE) $< -o $@ -l$(VERSION)
 
 # Compile all object files
 	$(COMPILE) -c $< -o $@
 
 # Create the ABACUS library
-lib$(VERSION).a : $(OBJECTS)
-	ar -cr lib$(VERSION).a $(OBJECTS)
-	mv lib$(VERSION).a $(LIB_DIR)/
-
+$(LIB_DIR)/lib$(VERSION).a : $(OBJECTS)
+	ar -cr $(LIB_DIR)/lib$(VERSION).a $(OBJECTS)
 
 ###########################################
 # Cleanup