clang-cl C++20 modules compile test

clang/test/Driver/cl-cxx20-modules.cppm

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+// REQUIRES: system-windows
+
+// RUN: rm -rf %t
+// RUN: mkdir -p %t
+// RUN: split-file %s %t
+
+// RUN: %clang_cl /std:c++20 --precompile "%/t/Hello.cppm" "/Fo%/t/Hello.pcm"
+// RUN: %clang_cl /std:c++20 %/t/use.cpp -fmodule-file=Hello=%/t/Hello.pcm %/t/Hello.pcm /Fo%/t/SimpleHelloWorld.exe 2>&1
+
+// RUN: %/t/SimpleHelloWorld.exe
+// CHECK: Simple Hello World!
+
+//--- Hello.cppm
+module;
+#include <iostream>
+export module Hello;
+export void hello() {
+  std::cout << "Simple Hello World!\n";
+}
+
+//--- use.cpp
+import Hello;
+int main() {
+  hello();
+  return 0;
+}
+
+//--- M.cppm
+export module M;
+export import :interface_part;
+import :impl_part;
+export void Hello();
+
+//--- interface_part.cpp
+export module M:interface_part;
+export void World();
+
+//--- impl_part.cppm
+module;
+#include <iostream>
+#include <string>
+module M:impl_part;
+import :interface_part;
+
+std::string W = "World!";
+void World() {
+  std::cout << W << std::endl;
+}
+
+//--- Impl.cpp
+module;
+#include <iostream>
+module M;
+void Hello() {
+  std::cout << "Complex Hello ";
+}
+
+//--- User.cpp
+import M;
+int main() {
+  Hello();
+  World();
+  return 0;
+}
+