[golang/go] x/build: add darwin/amd64 builders with macOS 15 (macOS Sequoia)

### ROOT CAUSE The Go CI system does not currently include a builder for the `darwin/amd64` architecture running on macOS 15 (Sequoia). This is necessary for building and testing Go on the latest macOS version for the `amd64` architecture, which is required for cross-compilation and ensuring compatibility with Intel-based Macs. ### CODE FIX To add the builder, the following changes are required in the CI configuration: 1. **Add a new builder definition** in the CI configuration file (if the CI system uses YAML, an example might be): ```yaml builders: - name: darwin-amd64-macos15 arch: amd64 os: darwin osversion: 15 # Additional configuration as required by the CI system ``` 2. **Set up a macOS 15 (Sequoia) environment** on the builder machine. This may require access to Apple silicon Macs (since macOS 15 is only available on Apple silicon Macs) or using a virtual machine that runs on Apple silicon. 3. **Integrate the builder into the CI pipeline** to run the necessary build and test commands. This might involve updating the CI scripts to include the new builder and ensuring it can cross-compile for other platforms if needed. 4. **Update the Go project's CI configuration** to include the new builder. This would typically be done in the Go CI repository (e.g., `golang.org/x/build`). 5. **Test the new builder** by running the Go build and test commands to ensure it works correctly with macOS 15. Note: The exact implementation may vary based on the specific CI system used by the Go project (e.g., Bazel, Jenkins, or custom scripts). The Go team would need to update their infrastructure accordingly.