Add dependencies for top-level build script

[alexcrichton]

Helps avoid unnecessarily compiling the main library!

[kureuil]

Isn't this supposed to be TEST_DATABASE_URL ? :)

[alexcrichton]

Oops indeed!

[carols10cents]

awesome!!! thanks!!

bors: r+

[bors-voyager]

Build succeeded

• continuous-integration/travis-ci/push

[jtgeibel]

I've just tested this locally, by: running cargo test, adding a migration, and running cargo test again. My new migration was not run.

I've added the following to the build script, which works for my simple test, but I'm not sure it is a complete solution:

println!("cargo:rerun-if-changed=migrations/");

Here are the reasons I think this may not be complete:

• The build script documentation notes that the behavior of timestamps on directories can be platform specific. However, I'm not aware of what those differences may be.
• The documentation notes that the directory is not traversed to check for additional timestamp changes. We can manually walk the tree and add a line for each directory and file, but I'm not certain that is necessary for this use case. If someone changes a migration during development (after running the initial migration), then they will need to run diesel migration redo before running cargo test anyway.

Thoughts?

[carols10cents]

@jtgeibel I would like a pull request for that please, I think it'll be good enough for most of the cases!