version: use OSS repo's version when building.

When building with redo, also include the git commit hash
from the proprietary repo, so that we have a precise commit
that identifies all build info (including Go toolchain version).

Add a top-level build script demonstrating to downstream distros
how to burn the right information into builds.

Adjust `tailscale version` to print commit hashes when available.

Fixes #841.

Signed-off-by: David Anderson <danderson@tailscale.com>

control/controlclient/direct.go

@@ -206,7 +206,7 @@ func NewHostinfo() *tailcfg.Hostinfo {
 		osv = osVersion()
 	}
 	return &tailcfg.Hostinfo{
-		IPNVersion: version.LONG,
+		IPNVersion: version.Long,
 		Hostname:   hostname,
 		OS:         version.OS(),
 		OSVersion:  osv,