`presubmit` option broken (race condition?)

After making code changes, when running `./gradlew presubmit` for the first time, it often fails with the following error:
```
foo/bar/some/file.java: formatted successfully

> Task :mobly-snippet-lib:openLintReport
The file /Users/angli/Developer/mobly-snippet-lib/third_party/sl4a/build/reports/lint-results.html does not exist.

FAILURE: Build failed with an exception.

* What went wrong:
Execution failed for task ':mobly-snippet-lib:openLintReport'.
> Process 'command 'open'' finished with non-zero exit value 1
```

Immediately run the presubmit command again, it passes.

Seems like there might be a race condition between the formatting task, the linter page generation, and the lint page opening.

@kdart