Calling JsStopDebugging() hits failfast in DebugContext.cpp

[fatcerberus]

Upon calling JsStopDebugging() on shutdown with a debugger attached, I was hitting (what seemed to be) a segfault somewhere inside ChakraCore.dll. After compiling the engine from master with debug symbols, I tracked down the location of the crash to the AssertOrFailFast call here:

• https://github.com/microsoft/ChakraCore/blob/master/lib/Runtime/Debug/DebugContext.cpp#L359

Seems to be something to do with internal handling of generators in the debugger. As far as I can tell I'm shutting down properly, so there doesn't seem to be anything I can do to work around the issue. For now I've reverted to ChakraCore 1.11.8 which doesn't appear to have this issue.