[libclc] [libclc][CMake] Check SOURCES and LIBRARIES arguments are not empty (PR #186542)

[Wenju He via cfe-commits]

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wenju-he wrote:

> This comment is outdated right

thanks, address it in https://github.com/llvm/llvm-project/pull/186544

https://github.com/llvm/llvm-project/pull/186542