compiler: stop iterator on error

If there is an error reading or parsing an archive header, the
Archive_iterator code would return a dummy header but would not mark
itself as done.  The effect is that an invalid archive leads to an
endless loop reading and re-reading the same archive header.  Avoid
that by setting the offset to the end of the file, which will cause
the iterator to == archive_end.

No test since it doesn't seem worth constructing an invalid archive.

Change-Id: I24eba41a2cd17e0d69ed95ea4e40a8d8a2661d10
Reviewed-on: https://go-review.googlesource.com/c/158217
Reviewed-by: Cherry Zhang <cherryyz@google.com>
diff --git a/go/import-archive.cc b/go/import-archive.cc
index a6d5403..868def7 100644
--- a/go/import-archive.cc
+++ b/go/import-archive.cc
@@ -780,6 +780,7 @@
                                      &this->next_off_))
 	{
 	  this->header_.off = filesize;
+	  this->off_ = filesize;
 	  return;
 	}
       this->header_.off = this->off_;