Add a test for the -fmodule-output BMI output file

Author: sharadhr

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

@@ -14,3 +14,11 @@
 
 //--- test.pcm
 // CPP20WARNING-NOT: clang-cl: warning: argument unused during compilation: '/std:c++20' [-Wunused-command-line-argument]
+
+// test whether the following outputs %Hello.bmi
+// RUN: %clang_cl /std:c++20 --precompile -x c++-module -fmodule-output=%t/Hello.bmi -Fo"%t/Hello.bmi" -c %t/Hello.cppm -### 2>&1 | FileCheck %s
+// CHECK: "-emit-module-interface"
+// CHECK: "-o" "{{.*}}Hello.bmi"
+
+//--- Hello.cppm
+export module Hello;