Hello :)

With the fix for bazelbuild/bazel#8330 we discovered one flaw in our design of Go cross compilation. Currently rules_go depend on C++ toolchain in //go/private:context.bzl (toolchains = ["@bazel_tools//tools/cpp:toolchain_type"]). This dependency exists no matter if we actually have C++ dependencies or not.

The problem is that with bazelbuild/bazel#8330 C++ autoconfigured toolchains properly report their constraints, and now Bazel detects that we don't actually have a C++ cross-compilation toolchain available. As a result the cross-compilation build of go fails:

ERROR: While resolving toolchains for target @io_bazel_rules_go//:go_context_data: no matching toolchains found for types @bazel_tools//tools/cpp:toolchain_type
ERROR: Analysis of target '//:main' failed; build aborted: no matching toolchains found for types @bazel_tools//tools/cpp:toolchain_type

To reproduce, create a hello world go_binary, and build it with bazel build //:hello_world --platforms=@io_bazel_rules_go//go/toolchain:darwin_amd64 on linux, (or if you're on mac, use a different platform).