configure_make should have instructions how to get at the built binaries

It would be nice to have an example of how one can reference a binary named in `configure_make.out_binaries`.

This is useful if you want to use such a built binary in a toolchain definition. You'd have:

Say I have:

```
configure_make(
name = "t"
# ...
out_binaries = [ "foo" ],
)
```

How do I invoke the built `foo` from say within a build rule?

It seems that `t.output_groups` has something useful, but extracting content from there seems clunky.

In any case, it would seem useful to have that documented in https://bazelbuild.github.io/rules_foreign_cc/main/configure_make.html

https://github.com/bazelbuild/rules_foreign_cc/issues/376 has some useful information, but ideally this would be front and center in the official docs.

Start with the configure_make documentation at bazelbuild.github.io/rules_foreign_cc/main/configure_make.html and review issue 376 for the existing information about out_binaries and output_groups. Document a clear example showing how a binary named in configure_make.out_binaries can be referenced from a build rule, with the finished page making the invocation path understandable.

Written by the indexing model from the issue text.