Properly set EXTRALIBS

(fixes compilation of shared libswscale on cygwin and other platforms)

Originally committed as revision 20413 to svn://svn.mplayerhq.hu/mplayer/trunk/libswscale

libswscale/Makefile

@@ -7,6 +7,8 @@ LIBVERSION=$(SWSVERSION)
 LIBMAJOR=$(SWSMAJOR)
 endif
 
+EXTRALIBS := -L$(BUILD_ROOT)/libavutil -lavutil$(BUILDSUF) $(EXTRALIBS)
+
 OBJS= swscale.o rgb2rgb.o yuv2rgb.o
 ifeq ($(TARGET_ALTIVEC),yes)
 OBJS+=  yuv2rgb_altivec.o