update makefile

Makefile

@@ -2,16 +2,16 @@ SRC:=src/*.cpp
 INCLUDE:=include/
 BUILD:=build
 FEATURES?=-DFIXED_ROW_SIZE=24
-CFLAGS:= $(FEATURES) -Wall -pedantic -O3 -march=native --std=gnu++20 -fgraphite -flto
-LFLAGS:=-O3 -flto -lfmt
-DESTDIR?=/usr/local/bin
+CXXFLAGS+= $(FEATURES) -Wall -pedantic -O3 -march=native --std=gnu++20 -fgraphite -flto
+LDFLAGS+=-O3 -flto -lfmt
+bindir?=/usr/local/bin
 
 hexview:
-	g++ $(SRC) $(CFLAGS) -I$(INCLUDE) -o $(BUILD)/$@ $(LFLAGS)
+	g++ $(SRC) $(CXXFLAGS) -I$(INCLUDE) -o $(BUILD)/$@ $(LDFLAGS)
 	strip $(BUILD)/$@
 
 clean:
 	rm -f $(BUILD)/*
 
 install:
-	cp -f $(BUILD)/hexview $(DESTDIR)/hexview
+	cp -f $(BUILD)/hexview $(DESTDIR)$(bindir)/hexview