Fix support for Xcode 9 -> 10.2

[frederoni]

Upgraded to CircleCI 2.1

Running tests on
Xcode 9.4.1 iOS 9.3
Xcode 10.0 iOS 12.0
Xcode 10.2 iOS 12.2

Despite the branch name, this PR doesn't migrate to Swift 5, it merely validates compatibility with various versions of Xcode.

cc @1ec5

[frederoni]

Even locally, 2 seconds did timeout 1/16 times for the 3.2 MB GeoJSON

[1ec5]

Yikes, somehow I didn’t realize our test fixtures were that big. This isn’t a performance test, so we should probably think about breaking this test case up into minimal test cases the next time we need to fix it.

[1ec5]

Suggested changelog entry:

• Fixed compatibility issues with Xcode 10.2 when the SDK is installed using Carthage. (#363)

[1ec5]

Is there a PR for this change or something else we can keep track of for when master gets updated? AliSoftware/OHHTTPStubs#295 is already in v7.0.0; is this for something else?

[1ec5]

Oh, looks like this commit also pulls in AliSoftware/OHHTTPStubs#286. The CircleCI configuration isn’t testing on watchOS anyways. So I think we can pin to the main pod’s v7.x.

[frederoni]

Yea, the reason why I switched to the fork here is the missing watchOS scheme in the original. We don't test on watchOS but we do compile for watchOS. We could switch back but it would require a workaround to run carthage bootstrap and ignore the .private and .resolved files.

[1ec5]

Yikes, somehow I didn’t realize our test fixtures were that big. This isn’t a performance test, so we should probably think about breaking this test case up into minimal test cases the next time we need to fix it.