opengl: Makefile.am: compile filter_draw on OSX

modules/video_output/opengl/Makefile.am

@@ -78,6 +78,10 @@ if HAVE_GL
 libglfilter_draw_plugin_la_LIBADD = libvlc_opengl.la $(GL_LIBS)
 vout_LTLIBRARIES += libglfilter_draw_plugin.la
 endif
+if HAVE_OSX
+libglfilter_draw_plugin_la_LIBADD = libvlc_opengl.la
+vout_LTLIBRARIES += libglfilter_draw_plugin.la
+endif
 if HAVE_IOS
 libglfilter_draw_plugin_la_LIBADD = libvlc_opengles.la $(GLES2_LIBS)
 libglfilter_draw_plugin_la_CFLAGS = -DUSE_OPENGL_ES2=1