Add E2E test for exposing public enums from ObjC to Swift

[polac24]

Part I of fixing #140 - E2E test that covers a scenario reported in the issue:

• Mixed target (ObjC+Swift) exposes an enum defined in ObjC (using NS_ENUM)
• Swift API uses that enum in the public API (using Bridging header) so -Swift.h contains an absolute path to the Bridging header.
• XCRemoteCache stores a plain -Swift.h content in an artifact, the build may fail if a local machine has a different absolute SRCROOT than the producer
• To emulate different SRCROOT machines, E2E test temporarily moves the directory of e2eTests/StandaloneSampleApp

This Standalone test is failing (as expected, the fix will be added in separate PRs) - for now, CI does not invoke it.
To run it locally, call rake e2e:run_standalone

This PR contains 2 changes/fixes to the E2E tests:

• prints xcodebuild output to the std - that could simplify troubleshooting CI errors
• small fix in valide_hit_rate