Improve variable names

Makefile

@@ -15,15 +15,15 @@ OBJ-DIR = $(BUILD-DIR)/obj
 TEST-DIR = $(BUILD-DIR)/test
 
 ifeq ($(FC),nvfortran)
-	MOD-OUT-OPTION = -module $(MOD-DIR)
+	MOD-OUTPUT = -module $(MOD-DIR)
 else
-	MOD-OUT-OPTION = -J$(MOD-DIR)
+	MOD-OUTPUT = -J$(MOD-DIR)
 endif
 
 ifeq ($(FC),nvfortran)
-	MOD-IN-OPTION = -module $(MOD-DIR)
+	MOD-INPUT = -module $(MOD-DIR)
 else
-	MOD-IN-OPTION = -I$(MOD-DIR)
+	MOD-INPUT = -I$(MOD-DIR)
 endif
 
 .PHONY: all test clean
@@ -32,12 +32,12 @@ all: $(STATIC)
 
 $(STATIC): $(SRC)
 		mkdir -p $(MOD-DIR) $(OBJ-DIR)
-		$(FC) $(FFLAGS) -c $(SRC) $(MOD-OUT-OPTION) -o $(OBJ-DIR)/$(FILENAME).o
+		$(FC) $(FFLAGS) -c $(SRC) $(MOD-OUTPUT) -o $(OBJ-DIR)/$(FILENAME).o
 		$(AR) $(ARFLAGS) $(STATIC) $(OBJ-DIR)/$(FILENAME).o
 
 test: $(TEST-SRC) $(STATIC)
 		mkdir -p $(TEST-DIR)
-		$(FC) $(FFLAGS) $(TEST-SRC) $(MOD-IN-OPTION) -o $(TEST-DIR)/test.out $(STATIC)
+		$(FC) $(FFLAGS) $(TEST-SRC) $(MOD-INPUT) -o $(TEST-DIR)/test.out $(STATIC)
 		$(TEST-DIR)/test.out
 
 clean: