GSubprocessLauncher: Crashes on Win64 when setting a custom environment
When setting a custom environment, GSubprocessLauncher will call _wspawnvpe()
which crashes with an Access Violation. My working assumption is that the environment copy is not done as Windows expects it.
This is probably one of the reasons why the subprocess tests fail wit MSVC.
I've reproduced this with the 2-58 and 2-60 branches.