Fix detection of Go 1.10.x

[dveeden]

Fedora 28 ships with go 1.10.x which build.sh detects as too old, while it isn't too old.
This PR fixes that by a more restrictive regex.

$ go version
go version go1.10.1 linux/amd64

[dveeden]

Looks like this is a duplicate of #458

[shlomi-noach]

We would need a better method, because the version could be 1.8 or 1.9 (no trailing .).

I have something else in mind, let me push a change.

[shlomi-noach]

I pushed a change to your PR, and it should be good now: explicitly allowing go1.8, go1.9, go1.10, and anything else is disallowed.