simplify vhook/*.o rule

Originally committed as revision 12682 to svn://svn.ffmpeg.org/ffmpeg/trunk

Makefile

@@ -49,9 +49,6 @@ $(PROGS): %$(EXESUF): %_g$(EXESUF)
 	cp -p $< $@
 	$(STRIP) $@
 
-vhook/%.o: vhook/%.c
-	$(CC) $(VHOOKCFLAGS) -c -o $@ $<
-
 .depend: version.h $(PROGS_SRCS)
 
 # bandaid to disable triggering shared library installation routines
@@ -79,6 +76,8 @@ LIBS_drawtext$(SLIBSUF)        = `freetype-config --libs`
 
 VHOOKCFLAGS += $(VHOOKCFLAGS-yes)
 
+vhook/%.o: CFLAGS:=$(VHOOKCFLAGS)
+
 LDFLAGS-$(CONFIG_SWSCALE) += -L$(BUILD_ROOT)/libswscale
 LDFLAGS-$(CONFIG_AVFILTER) += -L$(BUILD_ROOT)/libavfilter
 LDFLAGS := $(LDFLAGS-yes) -L$(BUILD_ROOT)/libavdevice -L$(BUILD_ROOT)/libavformat -L$(BUILD_ROOT)/libavcodec -L$(BUILD_ROOT)/libavutil -g $(LDFLAGS)