Tao He authored Jan 26, 2018 and Andrey Mokhov committed Jan 26, 2018

* Support run GHC's test from hadrian.

1. Necessary command line arguments to run test driver.
   + `--test-only=<TEST_CASE>`
   + `--test-skip-perf`
   + `--test-summary=<SUMMARY_FILE>`
   + `--test-junit=<SUMMARY_FILE>`
   + `--test-config=<EXTRA_TEST_CONFIG>`
2. Synchronize configurations from test.mk.
3. Synchronize GHC's compilation flags from test.mk (that's very important).

* The `RunTest` builder and `test` rule to run GHC's test.
* Timeout rules.
* Reduce boilerplate.
* Fix warning.
* Move getTestArgs into Settings.Builders.RunTest.
* Drop `validate` related code to avoid confusion.
* Replace explicit `chmod +x` with `makeExecutable`.
* Fix executable's extension.