Weak-link Swift compatibility library in Tart releases (#1339)

* Bundle Swift compatibility libraries in Tart releases

* fix(release): weak-link Swift compatibility library

* fix(release): weak-link from Xcode 27 library path

.ci/build-release.sh

@@ -5,12 +5,15 @@ set -eu
 ARCH="$1"
 SCRATCH_PATH=".build/$ARCH"
 OUTPUT_PATH=".build/prebuilt/$ARCH"
+SWIFT_COMPATIBILITY_LIBRARY="$(dirname "$(xcrun --find swiftc)")/../lib/swift-6.2/macosx/libswiftCompatibilitySpan.dylib"
 
 swift build \
   --build-system swiftbuild \
   --scratch-path "$SCRATCH_PATH" \
   --arch "$ARCH" \
   --configuration release \
+  -Xlinker -weak_library \
+  -Xlinker "$SWIFT_COMPATIBILITY_LIBRARY" \
   --product tart
 
 BIN_PATH=$(swift build \