-CFLAGS = -Wall -Os -mcpu=arm1136jf-s -mthumb
-CPPFLAGS = -Wall `pkg-config --cflags dbus-glib-1`
-LDFLAGS = `pkg-config --libs dbus-glib-1`
-PREFIX = /usr/local
+CFLAGS = -Wall -Os $(EXTRA_CFLAGS)
+CPPFLAGS = `pkg-config --cflags dbus-glib-1` $(EXTRA_CPPFLAGS)
+LDFLAGS = `pkg-config --libs dbus-glib-1` $(EXTRA_LDFLAGS)
+PREFIX = /usr