Revert "[WASM] Always install CoreFoundation headers in target dir"

This reverts commit 50ec5f6.

Author: kateinoigakukun

utils/webassembly/build-foundation.sh

@@ -24,9 +24,17 @@ cmake -G Ninja \
 ninja -v
 ninja -v install
 
-mv $DESTINATION_TOOLCHAIN/usr/lib/swift_static/CoreFoundation \
-  $DESTINATION_TOOLCHAIN/usr/lib/swift/wasi/wasm32/CoreFoundation
+# On macOS the target CoreFoundation shadows the CoreFoundation suppplied by Xcode.
+# On Linux though there's no system CoreFoundation, its headers have to be shipped
+# in the installable archive and serve for both host and target.
+if [[ "$(uname)" == "Darwin" ]]; then
+  mv $DESTINATION_TOOLCHAIN/usr/lib/swift_static/CoreFoundation \
+    $DESTINATION_TOOLCHAIN/usr/lib/swift/wasi/wasm32/CoreFoundation
+else
+  mv $DESTINATION_TOOLCHAIN/usr/lib/swift_static/CoreFoundation \
+    $DESTINATION_TOOLCHAIN/usr/lib/swift/CoreFoundation
+fi
 
 # .swiftdoc and .swiftmodule files should live in `swift`, not in `swift_static`
 mv $DESTINATION_TOOLCHAIN/usr/lib/swift_static/wasi/wasm32/Foundation.swift* \
-  $DESTINATION_TOOLCHAIN/usr/lib/swift/wasi/wasm32
+  $DESTINATION_TOOLCHAIN/usr/lib/swift/wasi/wasm32