XCTest binaries on Linux/Windows should support `--dump-tests-json` and other experimental features

[cmcgee1024]

The binaries produced for the XCTests on these platforms now has a main symbol that runs, and it exits successfully. But, it doesn't support things like dumping the JSON list of the tests using the --dump-tests-json flag. Also, there are other common flags supported by these binaries if they are produced using the SwiftPM native build system.

They should support most of the common features, minus some of the experimental ones that are not really being used.

[cmcgee1024]

Possible duplicate issue is here: #393