xinput1_3 proxy under wine/proton prevents all controller input

[apple1417]

When running under wine, usually you'd set WINEDLLOVERRIDES="xinput1_3=n,b" to force the native version of the dll to be loaded - i.e. our proxy. However, even without our dll present, just setting this env var will prevent all controller input. It seems only the builtin xinput is actually functions (which kind of makes sense, since the controllers don't exist on the windows side).

This is not strictly a bug in our code, but it would be nice if there was some way we could proxy to the builtin xinput instead when running under proton.