[clang] [Clang][Cmake] fix libtool duplicate member name warnings (PR #133619)

[Nikita Popov via cfe-commits]

nikic wrote:

@farzonl Instructions in the sense of the instructions retired during compilation, not the number of instructions in the object file :)

I wouldn't expect the changes you made here to have any significant impact on build time. (I guess it might serialize the build more, maybe?)

https://github.com/llvm/llvm-project/pull/133619