[infra] Disable Goma on dartk-linux-release-riscv64-qemu.
[infra] Disable Goma on dartk-linux-release-riscv64-qemu.

This is faster than Goma's local fallback.

Change-Id: Ieedfaf773279270ed6138d189d3b6b5ab6bbc8d4
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/256242
Reviewed-by: William Hesse <a821cddceae7dc400f272e3cb1a72f400f9fed6d@google.com>
Commit-Queue: Ryan Macnak <d738b7f001baf9789095d7dc549cff6de60b011d@google.com>

dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk