Don't declare -lm as a dependency of swscale-example.

git-svn-id: file:///var/local/repositories/mplayer/trunk/libswscale@23140 b3059339-0415-0410-9bf9-f77b7e298cf2

Makefile

@@ -18,7 +18,8 @@ include ../common.mak
 
 cs_test: cs_test.o $(LIB)
 
-swscale-example: swscale-example.o $(LIB) -lm
+swscale-example: swscale-example.o $(LIB)
+swscale-example: EXTRALIBS += -lm
 
 clean::
 	rm -f cs_test swscale-example