Only output when tests/builds fail if --quiet flag is present

[clayellis]

Only output when tests and builds fail if the --quiet flag is present.

Motivation:

Resolves the latest conversation on #4395 concerning how the --quiet flag doesn't do what it advertises when used with swift test and swift build.

Modifications:

• When not testing in parallel, and --quiet is present, collect output until tests finish and print output to stdout conditionally.
• Pass LoggingOptions into ParallelTestRunner.
• Determine if any of the parallel tests failed and, if so, output all test results (regardless of passing status) if --quiet is present.
• Adds three new test fixtures (TestQuietPass, TestQuietPassFail, TestQuietFail) for testing the quiet flag
• Adds tests for the --quiet flag when all tests pass, when some tests pass/fail, when all tests fail.
• Redirect build output to a thread-safe buffered output stream that will be flushed to stdout if a build fails when --quiet is present.
• Adds tests for the --quiet flag when a build passes and when one fails.

Result:

If tests pass successfully and the --quiet flag is present, nothing will be output. Output as normal when tests fail. The only notable change to output in the failure case is that when running tests in parallel (--parallel), the progress animation is not updated.

If a build succeeds and the --quiet flag is present, nothing will be output. If a build fails with the flag, the build output will appear as normal on stdout.

[clayellis]

This is far enough along now that I think it's ready for review. I'd like some feedback on the approaches taken, whether they're in the right direction.

I'd still like to add a few more tests for swift build --quiet and to resolve the discrepancies between a failed build's output with and without the quiet flag. (See this comment.)

[MaxDesiatov]

@swift-ci test

[MaxDesiatov]

Overall this makes sense, but IMO it should avoid new uses of BufferedOutputByteStream and resolve a few line length formatting nits.

[MaxDesiatov]

@swift-ci test

[grynspan]

Does this change take swift-testing into account? If not, are there changes needed in swift-testing to support it?

[MaxDesiatov]

@swift-ci test

[MaxDesiatov]

@swift-ci test windows

[MaxDesiatov]

@swift-ci test windows

[MaxDesiatov]

The newly added tests need to be fixed on Linux for both swift build and ./Utilities/build-using-self, and on macOS only for the latter.

[MaxDesiatov]

Hi @clayellis, would you be able to resolve conflicts and address review feedback on this PR? Thanks!

[clayellis]

Yes, I'll aim to complete this PR by the end of the week (hopefully earlier.)