ci(testflight): add MetalToolchain cleanup for Xcode 26 Swift compatibility

Remove MetalToolchain assets before building to fix Swift compatibility library linking errors (swiftCompatibility56, swiftCompatibilityPacks). This is a known Xcode 26.0.1/26.1.1 issue where the MetalToolchain interferes with Swift library resolution.

Fixes linker errors: "Could not find or use auto-linked library 'swiftCompatibility56'"

Refs: actions/runner-images#13135
Refs: #5556

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

Author: antonis

.github/workflows/testflight.yml

@@ -21,6 +21,8 @@ jobs:
     steps:
       - uses: actions/checkout@8e8c483db84b4bee98b60c0593521ed34d9990e8 # v6
       - run: sudo xcode-select -s /Applications/Xcode_26.1.1.app/Contents/Developer
+      - name: Clean MetalToolchain to fix Swift compatibility libraries
+        run: sudo rm -rf /var/run/com.apple.security.cryptexd/mnt/com.apple.MobileAsset.MetalToolchain*/Metal.xctoolchain
       - uses: ruby/setup-ruby@v1
         with:
           working-directory: samples/react-native