Test with Xcode 10/iOS 12 betas on CircleCI

[friedbunny]

CircleCI has added an Xcode 10 (beta 5 😞) container and the release date for Xcode 10/iOS 12 is approaching (likely mid-September), so it’s about time we formally added a temporary job that exercises the new bits.

/cc @mapbox/maps-ios

[friedbunny]

I’ve been working on this and it seems like any test with a timeout can and will fail under Xcode 10 on CircleCI. Local tests are solid, but I’m seeing a variety of "Asynchronous wait failed: Exceeded timeout of x seconds” on CircleCI in:

• MGLMapViewLayoutTests.testOrnamentPlacement
• MGLOfflineStorageTests.testAddPackForBounds
• MGLStyleTests.testLayersOrder
• Others...

[julianrex]

@friedbunny wondering if we need to add explicit dependencies, similar to mapbox/ios-sdk-examples#221 (comment).

[friedbunny]

CircleCI has updated to Xcode 10 GM.

[friedbunny]

After bumping timeouts, most tests pass and don’t approach the new timeout limit (though some do, occasionally). Performance seems wildly variable with Xcode 10 tests on CI so far.

I’m also seeing PENDING tests fail, which doesn’t seem correct:

MBCameraTransitionTests
    ✗ testContinuallyResettingNorthInIsChangingPENDING, Asynchronous wait failed: Exceeded timeout of 1 seconds, with unfulfilled expectations: "Map view should finish loading style.".
    '-[MBCameraTransitionTests testContinuallyResettingNorthInIsChangingPENDING]' is a pending test - skipping
    '-[MBCameraTransitionTests testContinuallySettingCoordinateInIsChangingPENDING]' is a pending test - skipping
    ⧖ testContinuallySettingCoordinateInIsChanging [PENDING]

[friedbunny]

Finally a green run.