SubpassDescriptionBuilder::resolve_attachments Must null Out the Pointer if Slice Length is 0

[cwfitzgerald]

Currently the builder for the resolve attachments just takes the pointer of the slice of the resolve attachments. Unfortunately the spec requires this be a true null if there are no resolve attachments.

pResolveAttachments is NULL or a pointer to an array of colorAttachmentCount VkAttachmentReference structures defining the resolve attachments for this subpass and their layouts.

Which means the generated code should look something like:

    pub fn resolve_attachments(mut self, resolve_attachments: &'a [AttachmentReference]) -> Self {
        self.inner.color_attachment_count = resolve_attachments.len() as _;
		if self.inner.color_attachment_count != 0 {
        	self.inner.p_resolve_attachments = resolve_attachments.as_ptr();
		} else {
			self.inner.p_resolve_attachments = 0 as _;
        }
        self
    }

Unfortunately it is just this slice that needs that qualification added.

This has caused a real driver issue on mobile drivers.

[cwfitzgerald]

Not an ash bug, misread the spec. This is a driver bug, and per precedent, will be worked around a layer above ash.

[MarijnS95]

Related: #445