shims: set SDKROOT for Swift

Library/Homebrew/shims/mac/super/swift

@@ -0,0 +1,15 @@
+#!/bin/bash
+
+# Set SDKROOT to ensure it matches Homebrew's choice of SDK.
+
+# HOMEBREW_LIBRARY is set by bin/brew
+# HOMEBREW_SDKROOT is set by extend/ENV/super.rb
+# shellcheck disable=SC2154
+source "${HOMEBREW_LIBRARY}/Homebrew/shims/utils.sh"
+
+if [[ -z "${SDKROOT}" && -n "${HOMEBREW_SDKROOT}" ]]; then
+  export SDKROOT=${HOMEBREW_SDKROOT}
+fi
+
+try_exec_non_system "swift" "$@"
+safe_exec "/usr/bin/swift" "$@"