Hook for any successful build

It would be great to have a way to invoke an external command on successful build of crate or any dependency with at least the following info:

• target
• crate name
• source dir
• dest dir
• lib file (if not lib.rs)

For example, if I have the following manifest:

[package]
name = "foo"
on_build_success = "update_src_indexes.sh"

[dependencies.bar]
git="https://github.com/foo/bar"

[dependencies.baz]
git="https://github.com/foo/baz" 

On the first build when everything builds, that external tool will be called with:

• target=x86_64-apple-darwin, name=bar, source=~/.cargo/path_to_bar, dest=./target/path_to_bar_lib
• target=x86_64-apple-darwin, name=baz, source=~/.cargo/path_to_baz, dest=./target/path_to_baz_lib
• target=x86_64-apple-darwin, name=foo, source=., dest=./target/path_to_baz_lib

The idea is that after any rebuild to be able to do some external processing like indexing sources.

Review Cargo's build lifecycle and dependency handling in relation to the manifest hook described here. Determine how successful builds would invoke an external command for crates and dependencies, including the target, crate name, source directory, destination directory, and library file. Done means the hook behavior and argument contract are implemented and verified for the example scenarios.