Makefile: add install{,-udevrule} and uninstall

This is supposed to help distro packagers of ltunify.

Makefile

@@ -1,6 +1,14 @@
 override CFLAGS := -g -O2 -Wall -Wextra -D_FORTIFY_SOURCE=2 -fstack-protector --param ssp-buffer-size=4 $(CFLAGS)
+# for install-home
 BINDIR ?= $(HOME)/bin
 
+# for install and uninstall
+DESTDIR ?=
+bindir ?= /usr/local/bin
+udevrulesdir ?= /etc/udev/rules.d
+
+udevrule = 42-logitech-unify-permissions.rules
+
 %: %.c
 	$(CC) $(CFLAGS) -o $(OUTDIR)$@ $<
 
@@ -10,9 +18,19 @@ read-dev-usbmon: read-dev-usbmon.c hidraw.c
 
 ltunify: ltunify.c hidpp20.c
 
-.PHONY: all clean install-home
+.PHONY: all clean install-home install install-udevrule uninstall
 clean:
 	rm -f ltunify read-dev-usbmon hidraw
 
 install-home: ltunify
 	install -m755 -D ltunify $(BINDIR)/ltunify
+
+# System-wide installation
+install: ltunify install-udevrule
+	install -m755 -D ltunify $(DESTDIR)$(bindir)/ltunify
+
+install-udevrule: udev/$(udevrule)
+	install -m644 -D udev/$(udevrule) $(DESTDIR)$(udevrulesdir)/$(udevrule)
+
+uninstall:
+	$(RM) $(DESTDIR)$(bindir)/ltunify $(DESTDIR)$(udevrulesdir)/$(udevrule)

README.txt

@@ -33,7 +33,19 @@ Usage of USB debugger:
 
 Pairing tool (ltunify)
 ltunify allows you to pair new devices, unpair existing devices or view
-information for those devices. Run `ltunify --help` for available options.
+information for those devices. In order to build the ltunify binary and install
+it to `$HOME/bin/ltunify`:
+
+    make ltunify
+    make install-home
+
+If you intend to package ltunify or otherwise install it system-wide with a
+udevrule, you can use:
+
+    make ltunify
+    make install DESTDIR=$pkgdir bindir=/usr/bin udevrulesdir=/lib/udev/rules.d
+
+Once installed, run `ltunify --help` for available options.
 
 Usage of the pairing tool is pretty straight-forward. Example session: