Check object file size before archiving.
Check object file size before archiving.

On Windows, when goma is used, we found a case that an archive file has
0 byte object, though it is not 0 byte on disk.

I'm not sure the correct reason yet, however, we can consider the
following cases.
(1) goma returned before writing whole object. However, if so, this
    should happen also on non NaCl cases.
(2) Because of file system limitation or something, archiver cannot
    read object files sometimes just after close().
(3) build_nexe.py contains some bug which we don't know.

I was investigated (1) and (3), but I didn't find any skeptical code.
So, now I'm suspecting (2). So, let me add an experimental code to
check the object file size before archiving.

BUG=390764

Review URL: https://codereview.chromium.org/1021983002

sbc100/native_client,sbc100/native_client,sbc100/native_client,sbc100/native_client,sbc100/native_client,sbc100/native_client