Add `xcodebuild -runFirstLaunch` fallback for Metal toolchain installation documentation (#51631)

When setting up on macOS 26, `xcodebuild -downloadComponent
MetalToolchain` can fail if Xcode hasn't been initialized yet. Running
`xcodebuild -runFirstLaunch` first resolves this.

Release Notes:

- N/A
dbe3cc7ca2Joey Carpinelli committed on 3/17/2026, 9:41:59 AM· committed by GitHubparent5d7e10e
1 file changedLine totals unavailable