macOS Testing is broken with nightly toolchain

[jmschonfeld]

It appears the macOS run is broken, at least for runs that use a nightly toolchain. The "Install Swift toolchain via Swiftly" step fails with:

Run swiftly install main-snapshot
  swiftly install main-snapshot
  swiftly use main-snapshot
  shell: /bin/bash -e {0}
  env:
    DEVELOPER_DIR: /Applications/Xcode_26.4.app/Contents/Developer
    SWIFTLY_HOME_DIR: /Users/runner/.swiftly
    SWIFTLY_BIN_DIR: /Users/runner/.swiftly/bin
    SWIFTLY_TOOLCHAINS_DIR: /Users/runner/.swiftly/toolchains
Error: RunProgramError(exitCode: 1, program: "/usr/bin/xcrun", arguments: ["--show-sdk-path", "--sdk", "macosx"])
Swiftly is currently unlinked and will not manage the active toolchain. You can
run
the following command to link swiftly to the active toolchain:

    $ swiftly link


Fetching the latest main branch snapshot...
Error: Process completed with exit code 1.

https://github.com/swiftlang/swift-foundation/actions/runs/32396783384/job/96515349154