[clang] [clang][modules] Print library module manifest path. (PR #76451)

[Fangrui Song via cfe-commits]

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@@ -0,0 +1,15 @@
+// Test that -print-library-module-manifest-path finds the correct file.
+
+// RUN: %clang -print-library-module-manifest-path \
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MaskRay wrote:

A lot of new options do support only the `--` form. For `--print-*` options, many support both `-` and `--`. Since it's difficult to remember, I think supporting both for the new option is fine. 

https://github.com/llvm/llvm-project/pull/76451