Fix udev rules install rule.

Makefile.in

@@ -2,6 +2,7 @@ CFLAGS = @GCC_CFLAGS@
 
 prefix = @prefix@
 exec_prefix = @exec_prefix@
+udev_rules_dir = @sysconfdir@/udev/rules.d
 
 libs = libwayland-server.so libwayland.so
 clients = flower gears screenshot terminal
@@ -49,11 +50,11 @@ $(clients) : CFLAGS += @CLIENT_CFLAGS@
 $(clients) : LDLIBS += -L. -lwayland @CLIENT_LIBS@ -lrt
 
 install : $(libs)
-	install -d @libdir@ @libdir@/pkgconfig
+	install -d @libdir@ @libdir@/pkgconfig ${udev_rules_dir}
 	install $(libs) @libdir@
 	install wayland-server.pc wayland.pc @libdir@/pkgconfig
 	install wayland-client.h @includedir@
-	install 70-wayland.rules ${sysconfdir}/udev/rules.d
+	install 70-wayland.rules ${udev_rules_dir}
 
 clean :
 	rm -f $(clients) $(compositors) *.o *.so