[MLIR] Do not link mlir-cpu-runner with X86 libs

The three libs where recently added to the `mlir-cpu-runner`'s
`CMakeLists.txt` file. This prevent the runner to compile on other
platform (e.g. Power in my case).  Native codegen is pulled in
by the ExecutionEngine library, so this is redundant in any case.

Differential Revision: https://reviews.llvm.org/D75916