Skip clang-module test on main until we include swift-testing in the SDK

Author: kateinoigakukun

test/toolchain/clang-module.swift

@@ -1,3 +1,6 @@
 // RUN: rm -rf %t.dir
 // RUN: mkdir -p %t.dir
 // RUN: %{swift} build --package-path %S/Inputs/clang-module-example --scratch-path %t.dir --triple wasm32-unknown-wasi --static-swift-stdlib
+
+// Skipping this test on main until we include swift-testing in the SDK
+// XFAIL: scheme=main