[Concurrency] Make leaks testing use the leaks macos tool

[ktoso]

This is more reliable than the deinit printing which often is flaky when CI is slow etc.

Resolves rdar://174207235

Outputs are rather nice as well:

# | Process 8318: 453 nodes malloced for 55 KB
# | Process 8318: 0 leaks for 0 total leaked bytes.

And if we actually have a leak:

# | Process 82548: 5 leaks for 160 total leaked bytes.
# |
# | STACK OF 5 INSTANCES OF 'ROOT LEAK: <Something>':
# | 10  libsystem_pthread.dylib               0x18b01ec10 start_wqthread + 8
# | 9   libsystem_pthread.dylib               0x18b01fe84 _pthread_wqthread + 232
# | 8   libdispatch.dylib                     0x18ae7b120 _dispatch_worker_thread2 + 184
# | 7   libdispatch.dylib                     0x18ae7a980 _dispatch_root_queue_drain + 360
# | 6   libswift_Concurrency.dylib            0x100dbd578 swift_job_runImpl(swift::Job*, swift::SerialExecutorRef) + 188  Actor.cpp:2229
# | 5   libswift_Concurrency.dylib            0x100dbbfd0 swift::runJobInEstablishedExecutorContext(swift::Job*, swift::SerialExecutorRef, swift::TaskExecutorRef) + 228  Actor.cpp:238
# | 4   a.out                                 0x100d114e8 closure #1 in closure #1 in test_taskGroup_next() + 72
# | 3   a.out                                 0x100d10be0 Something.__allocating_init(int:) + 44
# | 2   libswiftCore.dylib                    0x102968bc4 swift_allocObject + 64  HeapObject.cpp:275
# | 1   libswiftCore.dylib                    0x102968744 swift_slowAlloc + 48  Heap.cpp:94
# | 0   libsystem_malloc.dylib                0x18ae50178 _malloc_zone_malloc_instrumented_or_legacy + 152
# | ====
# |     5 (160 bytes) << TOTAL >>
# |       1 (32 bytes) ROOT LEAK: <Something 0x827028060> [32]
# |       1 (32 bytes) ROOT LEAK: <Something 0x827028080> [32]
# |       1 (32 bytes) ROOT LEAK: <Something 0x8270280a0> [32]
# |       1 (32 bytes) ROOT LEAK: <Something 0x8270280c0> [32]
# |       1 (32 bytes) ROOT LEAK: <Something 0x8270280e0> [32]

etc

[ktoso]

@swift-ci please smoke test

[ktoso]

@swift-ci please smoke test

[mikeash]

Looks good, although it's unfortunate to lose coverage on other platforms. In practice there shouldn't be any cross-platform variation that would cause a leak only on some other platform.

[ktoso]

Yeah, unfortunately not great drop in equivalent on the other platforms 😢 We could make something but that'd be more work...

Thanks for review

[ktoso]

@swift-ci please smoke test

[ktoso]

@swift-ci please smoke test macOS

[ktoso]

@swift-ci please smoke test macOS platform

[ktoso]

Turns out this gets stuck on CI, likely due to leaks needing more permissions hm... Looking into it some more

[ktoso]

@swift-ci please smoke test

[ktoso]

Nope, this also doesn't work on CI.

[ktoso]

We may need to give up on leaks on CI and make this just some countdown latch style test.