This makes Sym flags consistent with the rest of the code after
the CL 37445.

No functional changes.

Passes toolstash -cmp.

Change-Id: Ica919f2ab98581371c717fff9a70aeb11058ca17
Reviewed-on: https://go-review.googlesource.com/37847Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>