macOS QXL VGA not available
Description of problem:
```
qemu-system-aarch64: QXL VGA not available
```
```
qemu-system-aarch64: -device qxl-vga: 'qxl-vga' is not a valid device model name
```
Steps to reproduce:
1. Build QEMU on macOS with SPICE support (meson)
2. Run commands listed above
3. Observe QXL not working
Additional information:
I'm wiring up QEMU SPICE support on Darwin for Nixpkgs. The same issue can be observed in macports qemu builds with spice. Could this be a packaging issue?