--@io_bazel_rules_go//go/config:tags cannot be provided multiple times

### What version of rules_go are you using?

v0.29.0

### What version of gazelle are you using?

v0.24.0

### What version of Bazel are you using?

5.0.0

### Does this issue reproduce with the latest releases of all the above?

yes

### What operating system and processor architecture are you using?

linux amd64

### Any other potentially useful information about your toolchain?

### What did you do?

bazel build //some/go:target --@io_bazel_rules_go//go/config:tags=a ----@io_bazel_rules_go//go/config:tags=b

### What did you expect to see?

Effectively, gotags would be `a` and `b`.

### What did you see instead?

Only one gotag appled.

I understand that one could do `--@io_bazel_rules_go//go/config:tags=a,b` but there are cases where one would want to inherit tags from `.bazelrc` or elsewhere.

Reproduce the reported Bazel build command with two --@io_bazel_rules_go//go/config:tags options and compare it with the single comma-separated form. Start by tracing how the go/config:tags option is parsed and inherited from .bazelrc or other configuration. Done means repeated options contribute both gotags, while existing single-value and comma-separated behavior remains intact.

Written by the indexing model from the issue text.