Working with directories in Bazel is discouraged since Bazel will not accurately track the directory contents, however, I often find myself
running into the same problem where the input to rule just has to be a directory. Most commonly, I am setting something like PATH, PYTHONPATH, RESOURCES, or TOOL_PATH in a rule’s env dictionary and these environment variables have to be either a single directory or column separated paths/directories.

This question suggests a workaround for genrule, but that approach does not work in rules like cc_binary since you cannot use bash builtins like realpath there.

Trivial example/MRE with cc_binary:

filegroup(
  name = "tool",
  srcs = ["tool1", "tool1_config"],
)

cc_binary(
    name = "example",
    srcs = ["example.cc"],
    env = {
        # does not work, this is the paths to the generated files not the directory
        "TOOL_PATH": "$(execpaths :tool)"
    },
)

What is the idiomatic way of solving this problem in general in Bazel?