Temporarily disable an Interop test on 32-bit

[atrick]

See rdar://102147255
(Swift CI: [main] 1. OSS - Swift (Tools Opt+Assert, Stdlib DebInfo+Assert, Test Device non_executable)
TEST 'Swift(watchos-armv7k) :: Interop/SwiftToC/structs/small-structs-pass-return-direct-in-c.swift' FAILED)

[atrick]

Merging to clear up CI and keep the bots free

[finagolfin]

Thanks, this was failing on the Android armv7 CI too before this workaround:

/home/ubuntu/jenkins/workspace/oss-swift-RA-linux-ubuntu-16.04-android/swift/test/Interop/SwiftToC/structs/small-structs-pass-return-direct-in-c.swift:30:16: error: CHECK-NEXT: expected string not found in input
// CHECK-NEXT: _Alignas(8) char _storage[16];
               ^
<stdin>:543:37: note: scanning from here
struct Structs_StructU16AndPointer {
                                    ^
<stdin>:544:2: note: possible intended match here
 _Alignas(4) char _storage[8];
 ^