Co-authored-by: Sandro <sandro.jaeckel@gmail.com>
- Use the 11.0 SDK instead of the 10.12 one on x86_64-darwin;
- Use `NIX_CFLAGS_COMPILE` and `NIX_LDFLAGS` to pass flags to the
compiler instead of patching the Xcode project files; and
- Use xcbuild to build the project.
While it’s unlikely, it’s possible that different MoltenVK versions
could require their own compatability patches. Support that by making
the `moltenvk` derivation provide the patch via `passthru`. There is no
package with the patch applied because the patch should never be used by
anything other than DXVK.
