Updated contrib packages for go1.13.5

["Steven Stallion" <sstallion@gmail.com>]

All,

I've added arm and 386 packages for go1.13.5 on 9p.io.  I decided to
package the entire GOROOT, so while the archive isn't particularly
large, it will take some time to install due to the number of files
contained within.

Assuming you have moved over to 9p.io for sources, you can install via
fgb's contrib by issuing:

% contrib/install stallion/go-$cputype

After installing this package, /$cputype/go/bin should be added to
/lib/namespace.local to add GOROOT to the default namespace.

By default, the go command will install binaries to $home/go/bin,
which may not be desirable for sites with multiple cputypes.  To avoid
this issue, user profiles should be amended to either set
GOBIN=$home/bin/$cputype or bind -c $home/bin/$cputype $home/go/bin.

Cheers,
Steve