Instead, use the `%target-swift-5.1-abi-triple` substitution to compile the tests
for deployment to the minimum OS versions required for use of _Concurrency APIs.
* Enable running tests from test/Concurrency/ directory in freestanding/minimal presets
* Mark failing Concurrency tests as XFAIL/SKIP on freestanding/minimal
The concurrency runtime now deploys back to macOS 10.15, iOS 13.0, watchOS 6.0, tvOS 13.0, which corresponds to the 5.1 release of the stdlib.
Adjust macro usages accordingly.
Rather than blanket-disabling concurrency tests when we aren't using a
just-built concurrency library, enable them whenever we have a
suitable concurrency runtime, either just-built, in the OS, or via the
back-deployment libraries.
This allows programs to target older OSes while using Concurrency behind an availability check. When targeting older OSes, the symbols are weak-linked and the compiler will require the use of Concurrency features to be guarded by an availability check.
rdar://75850003
The test has been flaky for the last couple of weeks. It almost always
fails, but from time to time the Windows VS2017 CI machine passes the
test.
Mark it as unsupported (since XFAIL will create random failures when the
test pass), to avoid noise in the CI machine.
