further protection from lame Solaris /bin/sh

extensions/Makefile.in

@@ -23,7 +23,8 @@ VPATH		= @srcdir@
 include $(DEPTH)/config/autoconf.mk
 
 ifdef MOZ_EXTENSIONS
-DIRS=$(MOZ_EXTENSIONS)
+# hack to make Solaris sh happy, until we can find a better solution
+DIRS=$(MOZ_EXTENSIONS) dummy
 endif
 
 include $(topsrcdir)/config/config.mk