Fix "GetThreadContext failed" on Windows
The version of bdwgc that Neko uses (7.6.0) can suddenly abort when GetThreadContext is called, if the thread is in protected code or an invalid state. One of the common culprits of this issue is antivirus programs.
This was fixed by Unity a few years ago, and included in the upstream 7.6 release line for 7.6.14.
This PR updates us to the latest bdwgc 7.6 release, 7.6.16.
Special thanks to @tobil4sk for helping resolve issues updating to the latest version.
For reference, here are some more details about the build changes: https://github.com/ivmai/bdwgc/issues/452
We might want to consider moving to 8.2 as suggested, because that way we can be more specific about what options we turn off. So long as there aren't any more build issues, of course.
We might want to consider moving to 8.2
Ubuntu 20.04 still has 7.6 so there is probably no point in doing this, especially with the potential breaking changes that come with a major version upgrade.
The azure pipelines error should have been resolved in master, so updating and solving the merge conflicts should fix the errors.
Pushed an update to resolve merge conflicts.