* Enable c-shared buildmode on darwin/386
* dyld does not support text relocation on i386. Add -read_only_relocs suppress flag to linker

Fixes #13904

Change-Id: I9adbd20d3f36ce9bbccf1bffb746b391780d088f
Reviewed-on: https://go-review.googlesource.com/18500Reviewed-by: David Crawshaw <crawshaw@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>