Platform linux/arm64 fails for build cache

[shahzzzam]

Describe the bug

The following task YAML fails:

version: v1.0.0
steps:
  - build: -t samashahtest.azurecr.io/acb:arm64  --platform linux/arm64 https://github.com/Azure/acr-builder.git
    cache: "enabled"

Fails with the error:

Error: failed to solve: rpc error: code = Unknown desc = failed to solve with frontend dockerfile.v0: failed to load LLB: runtime execution on platform linux/arm64 not supported
Usage:
  /buildx build [OPTIONS] PATH | URL | - [flags]

To Reproduce
Steps to reproduce the behavior:
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Expected behavior
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Screenshots
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Any relevant environment information

• OS: [e.g. Windows]
• Version [e.g. v1.0.0]

Additional context
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[shahzzzam]

Does not seem related specifically to this project. But created an issue for tracking purposes