Makefile: Make it more flexible...

* Add possibility to override compiler and CFLAGS
* Add possibility to use custom LDFLAGS for linking
* Add install target

Makefile

@@ -1,9 +1,19 @@
 TARGETS = xl710_unlock
 
+CC ?= gcc
+CFLAGS ?= -Wall -O2
+
+INST_DIR ?= /usr/sbin
+
+
 all: $(TARGETS)
 
 clean:
 	rm -f $(TARGETS)
 
 %:	%.c
-	gcc -Wall -O2 $< -o $@
+	$(CC) $(CFLAGS) $(LDFLAGS) $< -o $@
+
+install:
+	mkdir -p $(DESTDIR)/$(INST_DIR)
+	install -m 750 $(TARGETS) $(DESTDIR)/$(INST_DIR)