[clang] [clang-cl] Accept `cl`-style output arguments (`/Fo`, `-Fo`) for `--fmodule-output` (PR #121046)

[Hans Wennborg via cfe-commits]

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@@ -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
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zmodem wrote:

>From the doc:

> To generate a BMI for an importable module unit, use either the --precompile or -fmodule-output command line options.

Your test uses *both*, with the same filename passed to two different flags. This seems wrong to me.

https://github.com/llvm/llvm-project/pull/121046