dzn: More fixes

Another smattering of fixes across the compiler (including one minor nir fix), linker, and actual driver. With this series (and a few more WARP fixes that should hopefully hit NuGet soon) I'm seeing a 98.5% pass rate for Vulkan 1.0, though I don't expect WARP to reach 100% anytime soon; there's some uniformity issues with compute, and it looks like SM6.7 doesn't quite add everything we need when it comes to comparison sampling.