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

[Alexandre Ganea via llvm-commits]

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+100 ICON "subdir" "/icon-new.ico"
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aganea wrote:

Ah yes I see. I wonder if the following would work in another .test file:
```
# REQUIRES: llvm-driver, clang

# RUN: %llvm llvm-rc ...
```
That would only run under
`cmake ... -DLLVM_ENABLE_PROJECTS="llvm;clang" -DLLVM_TOOL_LLVM_DRIVER_BUILD=ON`
but I think it's fine we have other tests like this.

Not sure though if we support launching `clang` from `llvm-rc` like this, but that'd be a nice to have eventually!

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