Enable ProcessStrictHandleCheckPolicy on Windows

[nakst]

On Windows, ProcessStrictHandleCheckPolicy can be enabled with SetProcessMitigationPolicy to check that the plugin does not misuse HANDLEs in the Win32 API. This is not specific to CLAP, but I think it is a nice-to-have in a plugin validator nonetheless.

[robbert-vdh]

What does this do exactly? Microsoft's documentation doesn't specify what 'manipulating a handle that is not valid' entails. Does that mean that calling, say, CloseHandle on a handle that has already been closed or a null pointer would SIGABRT instead of returning false? I've never seen other applications (or other validators) use this, so I'm not quite sure what the use case is.

[nakst]

Does that mean that calling, say, CloseHandle on a handle that has already been closed or a null pointer would SIGABRT instead of returning false?

Yes, this is the general idea.

In the context of a multithreaded DAW with plugins, I think it is important to ensure that plugins do not have bugs of this form, since misuse of a handle by a plugin could affect the host itself as well as other plugins, resulting in e.g. file data corruption.

I've never seen other applications use this

I believe Windows enables it by default for all UWP applications.