Revert "[go] use the GOROOT in out/ for fuchsia bianries"

This reverts commit 7623f5dd0157697a19c3b3f9a78137a80bb8f141.

Reason for revert: broke fuchsia build

Original change's description:
> [go] use the GOROOT in out/ for fuchsia bianries
> 
> A separate GOROOT lets the host buildtools Go drift significantly
> from third_party/go. (Which is necessary if too long goes between
> rebases, as it has now.)
> 
> Change-Id: I4b334b69aae597b2eb16401d23341dc2e741e681

TBR=phosek@google.com,crawshaw@google.com

Change-Id: I123598d90b60e0f6b70bf48c328a422e2f2d8a2c
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
2 files changed