sysdeps test: Wait for spawned process to exit
On Windows, the "out" parameter for the process handle isn't set unless we specify G_SPAWN_FLAGS_DO_NOT_REAP_CHILD. That means we can't terminate it, and the child process is leaked. When running the test individually, the leaked process is harmless apart from its resource cost, but when running under CTest, it holds a file descriptor open (or something) which causes CTest to not exit.
If we do specify G_SPAWN_FLAGS_DO_NOT_REAP_CHILD, we become responsible for "reaping" the child process by waiting for its exit status, which is an OS-specific action.
Resolves: #238 (closed)
@rhabacker, please could you test this in real Windows?
Travis-CI was successful (same code, older commit message): https://travis-ci.org/smcv/dbus/builds/463830026