SDK registration no longer detecting go_download_sdk

[sluongng]

This PR broke buildbuddy repo when upgrading from v0.38.1 to v0.39.1.

ERROR: Traceback (most recent call last):
        File "/Users/sluongng/work/buildbuddy/buildbuddy/WORKSPACE", line 81, column 23, in <toplevel>
                go_register_toolchains(
        File "/private/var/tmp/_bazel_sluongng/06e573a93bc2d6a9cad4ad41f00b4310/external/io_bazel_rules_go/go/private/sdk.bzl", line 641, column 17, in go_register_toolchains
                fail('go_register_toolchains: version must be a string like "1.15.5" or "host"')
Error in fail: go_register_toolchains: version must be a string like "1.15.5" or "host"

Here is the bisect that I used

> cat test-build.sh
#!/bin/bash

(
  cd /Users/sluongng/work/buildbuddy/buildbuddy
  bazel build cli --override_repository=io_bazel_rules_go=/Users/sluongng/work/bazelbuild/rules_go
)

Bisect run

  cd /Users/sluongng/work/bazelbuild/rules_go
  git bisect start --first-parent
  git bisect bad HEAD # this is latest master (e558f56df9995f571e49de336c3831d407d9ff70)
  git bisect good v0.38.1
  git bisect run ./test-build.sh

Most likely this has something to do with how our repo is registering separate Go SDK using go_download_sdk calls to avoid some transition cross-compilation we found in the past. https://github.com/buildbuddy-io/buildbuddy/blob/ede1e1d07122a3bdd22a61b31dd7c6a8d8bd458d/WORKSPACE#L53-L83

cc: @fmeum @tyler-french

[fmeum]

I suspect that this line is now out-of-date:

rules_go/go/private/sdk.bzl

Line 642 in e558f56

sdk_kinds = ("_go_download_sdk", "_go_host_sdk", "_go_local_sdk", "_go_wrap_sdk")

@sluongng Could you check whether that's all that broke and potentially submit a PR?

[sluongng]

thanks for the hint, PR submitted 🤗