bitbake: dump_cache.py: use python3 as interpreter

Fixed:
  File "bitbake/contrib/dump_cache.py", line 39
    print("Error, need one argument!", file=sys.stderr)

(Bitbake rev: 435c6fb838b9f38c0477bcc2f07c8ce22999132b)

Signed-off-by: Robert Yang <liezhi.yang@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

bitbake/contrib/dump_cache.py

@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 # ex:ts=4:sw=4:sts=4:et
 # -*- tab-width: 4; c-basic-offset: 4; indent-tabs-mode: nil -*-
 #