fix disable KVM on arch architecture

[giper45]

No description provided.

[kroese]

Why?

[giper45]

Hi, I tried on arm64 (macOS M1) machine, it gives errors due to missing KVM device...
I though that this would be an error for arm-related machine that should disable kvm.
If kvm works for native arm, maybe this should be not performed. However, I know that you do not support macOS, but by disabling KVM (through this change, basically), it actually simply works for simple alpine setup.
If on arm Linux the behavior should be enable KVM, I could add an external KVM_DISABLE env to reach the purpose for macOS systems.

[kroese]

KVM works fine on ARM systems like the Raspberry Pi. It only doesnt work on Mac M1.

And there already exists an environment variable to disable it:

environment:
  KVM: "N"

It's even written in the error message that you can use that flag? And thats its not recommended because emulation is extremely slow that way.

[giper45]

Ah ok sorry, yes it appeared in the log, did not figure out that was related to Docker external environment variables.
I know about performance issues, but I would like to try to integrate the acceleration of Mac hvf ecc. by taking information from the UTM virtualization system.
BTW great project!