Search for go/gccgo during build

Change-Id: Ifb33613860d74e3f8a2787018f17f93aa4e4671d
Reviewed-on: http://review.couchbase.org/36203
Tested-by: Trond Norbye <trond.norbye@gmail.com>
Reviewed-by: Chris Hillery <ceej@couchbase.com>