Makefile: add install target

Makefile

@@ -7,6 +7,8 @@ endif
 
 -include config.mk
 
+PREFIX ?= /usr/local
+
 SRCS := shairport.c rtsp.c mdns.c common.c rtp.c player.c alac.c audio.c audio_dummy.c
 
 ifdef CONFIG_AO
@@ -16,6 +18,9 @@ endif
 # default target
 all: shairport
 
+install: shairport
+	install -m 755 shairport $(PREFIX)/bin/shairport
+
 shairport: $(SRCS)
 	$(CC) $(CFLAGS) $(SRCS) $(LDFLAGS) -o shairport