Build both static and shared libs from the same object.

This makes libpostproc consistent with all the other libraries.
patch by Diego 'Flameeyes' Pettenò, flameeyes gmail com

Originally committed as revision 11526 to svn://svn.ffmpeg.org/ffmpeg/trunk

libpostproc/Makefile

@@ -12,15 +12,9 @@ LIBMAJOR=$(SPPMAJOR)
 
 HEADERS = postprocess.h
 
-include ../common.mak
-
-$(LIBNAME): postprocess.o
-$(SLIBNAME_WITH_MAJOR): postprocess_pic.o
+OBJS = postprocess.o
 
-depend dep: postprocess.c
-
-postprocess_pic.o: postprocess.c
-	$(CC) -c $(CFLAGS) -fomit-frame-pointer -fPIC -DPIC -o $@ $<
+include ../common.mak
 
 uninstall-headers::
 	-rmdir "$(prefix)/include/postproc"