Now that darwin/arm supports position independent code, allow the
binaries generated by the c-archive tests be position independent
(PIE) as well.

Change-Id: If0517f06e92349ada29a4e3e0a951f08b0fcc710
Reviewed-on: https://go-review.googlesource.com/22841Reviewed-by: David Crawshaw <crawshaw@golang.org>
Run-TryBot: Elias Naur <elias.naur@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>