[llvm] [llvm-rc] Accept filenames provided as multiple string literals (PR #68881)

[Alexandre Ganea via llvm-commits]

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@@ -0,0 +1,2 @@
+100 ICON "subdir" "/icon-new.ico"
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aganea wrote:

Would it be better if a preprocessor definition was used here instead of `"subdir"`, and below in the test? Like shown in https://github.com/llvm/llvm-project/issues/51286? That would show the end-intention for someone who reads this patch later.

https://github.com/llvm/llvm-project/pull/68881