[adincebic]

This makes Swift tools from locally discovered toolchain available as labels.

It is similar to what we added for standalone toolchain in #1896.

To use this, we need to make repo available through module extension first:

local_swift = use_extension(
    "@rules_swift//swift:extensions.bzl",
    "local_toolchain",
)

use_repo(local_swift, "rules_swift_local_config")

Then we can bazel run available tools:

bazel run @rules_swift_local_config//:swift

The files are symlinks to the installed executables. Tools missing from
the installation, such as some LLVM tools in Xcode, have no exported label.

All available tools can be discovered by querying the repo:

bazel query '@rules_swift_local_config//:*'