Makefile.hw: allow hw/ files to include glib headers

Reviewed-by: Richard Henderson <rth@twiddle.net>
Signed-off-by: Avi Kivity <avi@redhat.com>

Makefile.hw

@@ -10,6 +10,7 @@ include $(SRC_PATH)/rules.mak
 $(call set-vpath, $(SRC_PATH):$(SRC_PATH)/hw)
 
 QEMU_CFLAGS+=-I..
+QEMU_CFLAGS += $(GLIB_CFLAGS)
 
 include $(SRC_PATH)/Makefile.objs