virtio-gpu-gl: "opengl is not available" message is too vague and doesn't suggest how to fix the problem
Description of problem:
I finally compiled qemu for Apple Silicon M2 Pro with opengl enabled and virtglrenderer enabled thanks to instruction from homebrew formula,
but I did it without homebrew nor macports just manually compiling necessary libraries.
Qemu was compiled succesfully with flags:
````
./configure --target-list=aarch64-softmmu,x86_64-softmmu --enable-cocoa  --enable-sdl --enable-virglrenderer --enable-vhost-net   --enable-spice-protocol --enable-tools --enable-opengl --enable-pixman --enable-vmnet
````

the device is clearly listed:
````
name "virtio-gpu-device", bus virtio-bus
name "virtio-gpu-gl-device", bus virtio-bus
name "virtio-gpu-gl-pci", bus PCI, alias "virtio-gpu-gl"
name "virtio-gpu-pci", bus PCI, alias "virtio-gpu"
````

So why it not working and gives that info while opengl is clearly there and is enabled.