Confusing output when code is compiling when running with "make --watch"

[jfmengels]

When running elm-test-rs make --watch, the output when the code is compiling is a bit unhelpful.

1. If you start running it when code compiles, it looks like it’s hanging (but it’s still doing things or it’s done). I would expect a message such as "Success! Compiled N modules." or just "Success!" to have some feedback and not feeling like the tool is in an infinite loop.

2. If after a change it’s compiling, then you have a large chunk of empty lines

Change detected in tests/Humio/Page/RepoOrView/SearchPage/FieldInteractionsTest.elm
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Change detected in tests/Humio/Page/RepoOrView/SearchPage/FieldInteractionsTest.elm
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I am not sure that these separators and blank spaces are worth having in this mode. Again, I would add a "Success!" message of some sorts at least.